From dc9ec6d13ee468433af018633771d1059e117420 Mon Sep 17 00:00:00 2001
From: Dominic Farolino <domfarolino@gmail.com>
Date: Sun, 5 May 2024 14:44:35 +0000
Subject: [PATCH] Spec the `first()` operator (#131)

SHA: 7a4c941f6bbf8b829b5185c4bc2cd78230dc7780
Reason: push, by domfarolino

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 index.html | 258 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 165 insertions(+), 93 deletions(-)

diff --git a/index.html b/index.html
index 4a82b2d..d5bda7a 100644
--- a/index.html
+++ b/index.html
@@ -6,7 +6,7 @@
   <link href="https://www.w3.org/StyleSheets/TR/2021/cg-draft" rel="stylesheet">
   <meta content="Bikeshed version 82ce88815, updated Thu Sep 7 16:33:55 2023 -0700" name="generator">
   <link href="https://wicg.github.io/observable/" rel="canonical">
-  <meta content="5ef367b3a03a02fe835bb2970d23b8aba10965fc" name="document-revision">
+  <meta content="7a4c941f6bbf8b829b5185c4bc2cd78230dc7780" name="document-revision">
 <style>
 /* Put nice boxes around each algorithm. */
 [data-algorithm]:not(.heading) {
@@ -901,7 +901,7 @@
   <div class="head">
    <p data-fill-with="logo"><a class="logo" href="https://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2021/logos/W3C" width="72"> </a> </p>
    <h1 class="p-name no-ref" id="title">Observable</h1>
-   <p id="w3c-state"><a href="https://www.w3.org/standards/types#CG-DRAFT">Draft Community Group Report</a>, <time class="dt-updated" datetime="2024-05-04">4 May 2024</time></p>
+   <p id="w3c-state"><a href="https://www.w3.org/standards/types#CG-DRAFT">Draft Community Group Report</a>, <time class="dt-updated" datetime="2024-05-05">5 May 2024</time></p>
    <div data-fill-with="spec-metadata">
     <dl>
      <dt>This version:
@@ -1173,10 +1173,11 @@ <h3 class="heading settled" data-level="2.2" id="observable-api"><span class="se
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise"><c- b>Promise</c-></a>&lt;<a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#idl-sequence" id="ref-for-idl-sequence"><c- b>sequence</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①②"><c- b>any</c-></a>>> <a class="idl-code" data-link-type="method" href="#dom-observable-toarray" id="ref-for-dom-observable-toarray"><c- g>toArray</c-></a>(<c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/toArray(options), Observable/toArray()" data-dfn-type="argument" data-export id="dom-observable-toarray-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-toarray-options-options"></a></dfn> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise①"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-undefined" id="ref-for-idl-undefined⑧"><c- b>undefined</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-foreach" id="ref-for-dom-observable-foreach"><c- g>forEach</c-></a>(<a data-link-type="idl-name" href="#callbackdef-visitor" id="ref-for-callbackdef-visitor"><c- n>Visitor</c-></a> <dfn class="idl-code" data-dfn-for="Observable/forEach(callback, options), Observable/forEach(callback)" data-dfn-type="argument" data-export id="dom-observable-foreach-callback-options-callback"><code><c- g>callback</c-></code><a class="self-link" href="#dom-observable-foreach-callback-options-callback"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions③"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/forEach(callback, options), Observable/forEach(callback)" data-dfn-type="argument" data-export id="dom-observable-foreach-callback-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-foreach-callback-options-options"></a></dfn> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise②"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-boolean" id="ref-for-idl-boolean②"><c- b>boolean</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-every" id="ref-for-dom-observable-every"><c- g>every</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate" id="ref-for-callbackdef-predicate①"><c- n>Predicate</c-></a> <dfn class="idl-code" data-dfn-for="Observable/every(predicate, options), Observable/every(predicate)" data-dfn-type="argument" data-export id="dom-observable-every-predicate-options-predicate"><code><c- g>predicate</c-></code><a class="self-link" href="#dom-observable-every-predicate-options-predicate"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions④"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/every(predicate, options), Observable/every(predicate)" data-dfn-type="argument" data-export id="dom-observable-every-predicate-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-every-predicate-options-options"></a></dfn> = {});
-  // Maybe? Promise&lt;any> first(optional SubscribeOptions options = {});
-  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise③"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①③"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-find" id="ref-for-dom-observable-find"><c- g>find</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate" id="ref-for-callbackdef-predicate②"><c- n>Predicate</c-></a> <dfn class="idl-code" data-dfn-for="Observable/find(predicate, options), Observable/find(predicate)" data-dfn-type="argument" data-export id="dom-observable-find-predicate-options-predicate"><code><c- g>predicate</c-></code><a class="self-link" href="#dom-observable-find-predicate-options-predicate"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑤"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/find(predicate, options), Observable/find(predicate)" data-dfn-type="argument" data-export id="dom-observable-find-predicate-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-find-predicate-options-options"></a></dfn> = {});
-  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise④"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-boolean" id="ref-for-idl-boolean③"><c- b>boolean</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-some" id="ref-for-dom-observable-some"><c- g>some</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate" id="ref-for-callbackdef-predicate③"><c- n>Predicate</c-></a> <dfn class="idl-code" data-dfn-for="Observable/some(predicate, options), Observable/some(predicate)" data-dfn-type="argument" data-export id="dom-observable-some-predicate-options-predicate"><code><c- g>predicate</c-></code><a class="self-link" href="#dom-observable-some-predicate-options-predicate"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑥"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/some(predicate, options), Observable/some(predicate)" data-dfn-type="argument" data-export id="dom-observable-some-predicate-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-some-predicate-options-options"></a></dfn> = {});
-  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise⑤"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①④"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-reduce" id="ref-for-dom-observable-reduce"><c- g>reduce</c-></a>(<a data-link-type="idl-name" href="#callbackdef-reducer" id="ref-for-callbackdef-reducer"><c- n>Reducer</c-></a> <dfn class="idl-code" data-dfn-for="Observable/reduce(reducer, initialValue, options), Observable/reduce(reducer, initialValue), Observable/reduce(reducer)" data-dfn-type="argument" data-export id="dom-observable-reduce-reducer-initialvalue-options-reducer"><code><c- g>reducer</c-></code><a class="self-link" href="#dom-observable-reduce-reducer-initialvalue-options-reducer"></a></dfn>, <c- b>optional</c-> <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑤"><c- b>any</c-></a> <dfn class="idl-code" data-dfn-for="Observable/reduce(reducer, initialValue, options), Observable/reduce(reducer, initialValue), Observable/reduce(reducer)" data-dfn-type="argument" data-export id="dom-observable-reduce-reducer-initialvalue-options-initialvalue"><code><c- g>initialValue</c-></code><a class="self-link" href="#dom-observable-reduce-reducer-initialvalue-options-initialvalue"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑦"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/reduce(reducer, initialValue, options), Observable/reduce(reducer, initialValue), Observable/reduce(reducer)" data-dfn-type="argument" data-export id="dom-observable-reduce-reducer-initialvalue-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-reduce-reducer-initialvalue-options-options"></a></dfn> = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise③"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①③"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-first" id="ref-for-dom-observable-first"><c- g>first</c-></a>(<c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑤"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/first(options), Observable/first()" data-dfn-type="argument" data-export id="dom-observable-first-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-first-options-options"></a></dfn> = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise④"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①④"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-last" id="ref-for-dom-observable-last"><c- g>last</c-></a>(<c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑥"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/last(options), Observable/last()" data-dfn-type="argument" data-export id="dom-observable-last-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-last-options-options"></a></dfn> = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise⑤"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑤"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-find" id="ref-for-dom-observable-find"><c- g>find</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate" id="ref-for-callbackdef-predicate②"><c- n>Predicate</c-></a> <dfn class="idl-code" data-dfn-for="Observable/find(predicate, options), Observable/find(predicate)" data-dfn-type="argument" data-export id="dom-observable-find-predicate-options-predicate"><code><c- g>predicate</c-></code><a class="self-link" href="#dom-observable-find-predicate-options-predicate"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑦"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/find(predicate, options), Observable/find(predicate)" data-dfn-type="argument" data-export id="dom-observable-find-predicate-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-find-predicate-options-options"></a></dfn> = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise⑥"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-boolean" id="ref-for-idl-boolean③"><c- b>boolean</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-some" id="ref-for-dom-observable-some"><c- g>some</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate" id="ref-for-callbackdef-predicate③"><c- n>Predicate</c-></a> <dfn class="idl-code" data-dfn-for="Observable/some(predicate, options), Observable/some(predicate)" data-dfn-type="argument" data-export id="dom-observable-some-predicate-options-predicate"><code><c- g>predicate</c-></code><a class="self-link" href="#dom-observable-some-predicate-options-predicate"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑧"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/some(predicate, options), Observable/some(predicate)" data-dfn-type="argument" data-export id="dom-observable-some-predicate-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-some-predicate-options-options"></a></dfn> = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise⑦"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑥"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-reduce" id="ref-for-dom-observable-reduce"><c- g>reduce</c-></a>(<a data-link-type="idl-name" href="#callbackdef-reducer" id="ref-for-callbackdef-reducer"><c- n>Reducer</c-></a> <dfn class="idl-code" data-dfn-for="Observable/reduce(reducer, initialValue, options), Observable/reduce(reducer, initialValue), Observable/reduce(reducer)" data-dfn-type="argument" data-export id="dom-observable-reduce-reducer-initialvalue-options-reducer"><code><c- g>reducer</c-></code><a class="self-link" href="#dom-observable-reduce-reducer-initialvalue-options-reducer"></a></dfn>, <c- b>optional</c-> <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑦"><c- b>any</c-></a> <dfn class="idl-code" data-dfn-for="Observable/reduce(reducer, initialValue, options), Observable/reduce(reducer, initialValue), Observable/reduce(reducer)" data-dfn-type="argument" data-export id="dom-observable-reduce-reducer-initialvalue-options-initialvalue"><code><c- g>initialValue</c-></code><a class="self-link" href="#dom-observable-reduce-reducer-initialvalue-options-initialvalue"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑨"><c- n>SubscribeOptions</c-></a> <dfn class="idl-code" data-dfn-for="Observable/reduce(reducer, initialValue, options), Observable/reduce(reducer, initialValue), Observable/reduce(reducer)" data-dfn-type="argument" data-export id="dom-observable-reduce-reducer-initialvalue-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-observable-reduce-reducer-initialvalue-options-options"></a></dfn> = {});
 };
 </pre>
    <p>Each <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable①⓪">Observable</a></code> has a <dfn class="dfn-paneled" data-dfn-for="Observable" data-dfn-type="dfn" data-noexport id="observable-subscribe-callback">subscribe callback</dfn>, which is a <code class="idl"><a data-link-type="idl" href="#callbackdef-subscribecallback" id="ref-for-callbackdef-subscribecallback①">SubscribeCallback</a></code> or a set of steps that take in a <code class="idl"><a data-link-type="idl" href="#subscriber" id="ref-for-subscriber①②">Subscriber</a></code>.</p>
@@ -1203,7 +1204,7 @@ <h3 class="heading settled" data-level="2.2" id="observable-api"><span class="se
    </div>
    <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concepts"><span class="secno">2.2.1. </span><span class="content">Supporting concepts</span><a class="self-link" href="#observable-supporting-concepts"></a></h4>
    <div class="algorithm" data-algorithm="default error algorithm">
-     The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="default-error-algorithm">default error algorithm</dfn> is an algorithm that takes an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑥">any</a></code> <var>error</var>, and runs
+     The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="default-error-algorithm">default error algorithm</dfn> is an algorithm that takes an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑧">any</a></code> <var>error</var>, and runs
   these steps: 
     <ol>
      <li data-md>
@@ -1217,10 +1218,10 @@ <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concept
    <dl>
     <dt data-md><dfn class="dfn-paneled" data-dfn-for="internal observer" data-dfn-type="dfn" data-noexport id="internal-observer-next-steps">next steps</dfn>
     <dd data-md>
-     <p>An algorithm that takes a single parameter of type <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑦">any</a></code>. Initially, these steps do nothing.</p>
+     <p>An algorithm that takes a single parameter of type <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑨">any</a></code>. Initially, these steps do nothing.</p>
     <dt data-md><dfn class="dfn-paneled" data-dfn-for="internal observer" data-dfn-type="dfn" data-noexport id="internal-observer-error-steps">error steps</dfn>
     <dd data-md>
-     <p>An algorithm that takes a single parameter of type <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑧">any</a></code>. Initially, the <a data-link-type="dfn" href="#default-error-algorithm" id="ref-for-default-error-algorithm">default error
+     <p>An algorithm that takes a single parameter of type <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⓪">any</a></code>. Initially, the <a data-link-type="dfn" href="#default-error-algorithm" id="ref-for-default-error-algorithm">default error
  algorithm</a>.</p>
     <dt data-md><dfn class="dfn-paneled" data-dfn-for="internal observer" data-dfn-type="dfn" data-noexport id="internal-observer-complete-steps">complete steps</dfn>
     <dd data-md>
@@ -1234,7 +1235,7 @@ <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concept
   are not provided via an <code class="idl"><a data-link-type="idl" href="#typedefdef-observerunion" id="ref-for-typedefdef-observerunion①">ObserverUnion</a></code> packed with Web IDL <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#dfn-callback-function" id="ref-for-dfn-callback-function②">callback functions</a>. See the <a href="#promise-returning-operators">§ 2.3.3 Promise-returning operators</a> that make use of this, for example.</p>
    </div>
    <div class="algorithm" data-algorithm="subscribe to an Observable" data-algorithm-for="Observable">
-     To <dfn class="dfn-paneled" data-dfn-for="Observable" data-dfn-type="dfn" data-noexport id="observable-subscribe-to-an-observable">subscribe to an <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable①⑥">Observable</a></code></dfn> given an <code class="idl"><a data-link-type="idl" href="#typedefdef-observerunion" id="ref-for-typedefdef-observerunion②">ObserverUnion</a></code>-or-<a data-link-type="dfn" href="#internal-observer" id="ref-for-internal-observer①">internal observer</a> <var>observer</var>, and a <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑧">SubscribeOptions</a></code> <var>options</var>, run
+     To <dfn class="dfn-paneled" data-dfn-for="Observable" data-dfn-type="dfn" data-noexport id="observable-subscribe-to-an-observable">subscribe to an <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable①⑥">Observable</a></code></dfn> given an <code class="idl"><a data-link-type="idl" href="#typedefdef-observerunion" id="ref-for-typedefdef-observerunion②">ObserverUnion</a></code>-or-<a data-link-type="dfn" href="#internal-observer" id="ref-for-internal-observer①">internal observer</a> <var>observer</var>, and a <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⓪">SubscribeOptions</a></code> <var>options</var>, run
   these steps: 
     <p class="note" role="note"><span class="marker">Note:</span> We split this algorithm out from the Web IDL <code class="idl"><a data-link-type="idl" href="#dom-observable-subscribe" id="ref-for-dom-observable-subscribe④">subscribe()</a></code> method, so that
   spec prose can <a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable③">subscribe</a> to an <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable①⑦">Observable</a></code> without going through the Web IDL bindings. See <a href="https://github.com/w3c/IntersectionObserver/issues/464">w3c/IntersectionObserver#464</a> for
@@ -1254,7 +1255,7 @@ <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concept
          <dt>If <var>observer</var> is a <code class="idl"><a data-link-type="idl" href="#callbackdef-subscriptionobservercallback" id="ref-for-callbackdef-subscriptionobservercallback③">SubscriptionObserverCallback</a></code>
          <dd>
           Set <var>internal observer</var>’s <a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps①">next steps</a> to these steps that take
-           an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any①⑨">any</a></code> <var>value</var>: 
+           an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②①">any</a></code> <var>value</var>: 
           <ol>
            <li data-md>
             <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function②">Invoke</a> <var>observer</var> with <var>value</var>.</p>
@@ -1265,7 +1266,7 @@ <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concept
          <dd>
           <ol>
            <li data-md>
-            <p>If <var>observer</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriptionobserver-next" id="ref-for-dom-subscriptionobserver-next②">next</a></code> is not null, set <var>internal observer</var>’s <a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps②">next steps</a> to these steps that take an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⓪">any</a></code> <var>value</var>:</p>
+            <p>If <var>observer</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriptionobserver-next" id="ref-for-dom-subscriptionobserver-next②">next</a></code> is not null, set <var>internal observer</var>’s <a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps②">next steps</a> to these steps that take an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②②">any</a></code> <var>value</var>:</p>
             <ol>
              <li data-md>
               <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function③">Invoke</a> <var>observer</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriptionobserver-next" id="ref-for-dom-subscriptionobserver-next③">next</a></code> with <var>value</var>.</p>
@@ -1273,7 +1274,7 @@ <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concept
  then <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/webappapis.html#report-the-exception" id="ref-for-report-the-exception④">report the exception</a> <var>E</var>.</p>
             </ol>
            <li data-md>
-            <p>If <var>observer</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriptionobserver-error" id="ref-for-dom-subscriptionobserver-error②">error</a></code> is not null, set <var>internal observer</var>’s <a data-link-type="dfn" href="#internal-observer-error-steps" id="ref-for-internal-observer-error-steps①">error steps</a> to these steps that take an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②①">any</a></code> <var>error</var>:</p>
+            <p>If <var>observer</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriptionobserver-error" id="ref-for-dom-subscriptionobserver-error②">error</a></code> is not null, set <var>internal observer</var>’s <a data-link-type="dfn" href="#internal-observer-error-steps" id="ref-for-internal-observer-error-steps①">error steps</a> to these steps that take an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②③">any</a></code> <var>error</var>:</p>
             <ol>
              <li data-md>
               <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function④">Invoke</a> <var>observer</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriptionobserver-error" id="ref-for-dom-subscriptionobserver-error③">error</a></code> with <var>error</var>.</p>
@@ -1315,7 +1316,7 @@ <h4 class="heading settled" data-level="2.2.1" id="observable-supporting-concept
       </dl>
      <li data-md>
       <p>If <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal②">signal</a> is <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted">aborted</a>, then <a data-link-type="dfn" href="#close-a-subscription" id="ref-for-close-a-subscription③">close</a> <var>subscriber</var>.</p>
-      <p class="note" role="note"><span class="marker">Note:</span> This can happen when <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions⑨">SubscribeOptions</a></code>'s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②">signal</a></code> is already <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted①">aborted</a>.</p>
+      <p class="note" role="note"><span class="marker">Note:</span> This can happen when <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①①">SubscribeOptions</a></code>'s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②">signal</a></code> is already <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted①">aborted</a>.</p>
      <li data-md>
       <p>Otherwise, <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-add" id="ref-for-abortsignal-add">add the following abort algorithm</a> to <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal③">signal</a>:</p>
       <ol>
@@ -1395,7 +1396,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
   with the <var>observable</var> returned from this method. Rather, the <var>observable</var> will continue to
   mirror <var>sourceObservable</var> uninterrupted.</p>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⓪">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑤">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①②">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑤">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable⑤">Subscribe</a> to <var>notifier</var> given <var>notifierObserver</var> and <var>options</var>.</p>
        <li data-md>
@@ -1466,7 +1467,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
           <p>Run <var>subscriber</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriber-complete" id="ref-for-dom-subscriber-complete⑥">complete()</a></code> method.</p>
         </dl>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①①">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑥">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①③">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑥">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable⑦">Subscribe</a> to <var>sourceObservable</var> given <var>sourceObserver</var> and <var>options</var>.</p>
       </ol>
@@ -1517,7 +1518,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
           <p>Run <var>subscriber</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriber-complete" id="ref-for-dom-subscriber-complete⑦">complete()</a></code> method.</p>
         </dl>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①②">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑤">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑦">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①④">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑤">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑦">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable⑧">Subscribe</a> to <var>sourceObservable</var> given <var>sourceObserver</var> and <var>options</var>.</p>
       </ol>
@@ -1564,7 +1565,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
           <p>Run <var>subscriber</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriber-complete" id="ref-for-dom-subscriber-complete①⓪">complete()</a></code> method.</p>
         </dl>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①③">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑥">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑧">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑤">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑥">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑧">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable⑨">Subscribe</a> to <var>sourceObservable</var> given <var>sourceObserver</var> and <var>options</var>.</p>
       </ol>
@@ -1608,7 +1609,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
           <p>Run <var>subscriber</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscriber-complete" id="ref-for-dom-subscriber-complete①①">complete()</a></code> method.</p>
         </dl>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①④">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑦">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑨">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑥">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑦">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal⑨">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable①⓪">Subscribe</a> to <var>sourceObservable</var> given <var>sourceObserver</var> and <var>options</var>.</p>
       </ol>
@@ -1636,7 +1637,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
        <li data-md>
         <p>Let <var>outerSubscriptionHasCompleted</var> to a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean">boolean</a>, initially false.</p>
        <li data-md>
-        <p>Let <var>queue</var> be a new <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#list" id="ref-for-list①">list</a> of <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②②">any</a></code> values, initially empty.</p>
+        <p>Let <var>queue</var> be a new <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#list" id="ref-for-list①">list</a> of <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②④">any</a></code> values, initially empty.</p>
         <p class="note" role="note"><span class="marker">Note:</span> This <var>queue</var> is used to store any <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable②⑧">Observable</a></code>s emitted by <var>sourceObservable</var>,
   while <var>observable</var> is currently subscribed to an <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable②⑨">Observable</a></code> emitted earlier by <var>sourceObservable</var> that has not yet been exhausted.</p>
        <li data-md>
@@ -1666,7 +1667,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
                <p>Note: This <a data-link-type="dfn" href="#flatmap-process-next-value-steps" id="ref-for-flatmap-process-next-value-steps①">flatmap process next value steps</a> will subscribe to the <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable③①">Observable</a></code> derived from <var>value</var> (if one such can be derived) and keep
    processing values from it until its subscription becomes inactive (either by
    error or completion). If this "inner" <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable③②">Observable</a></code> completes, then the
-   processing steps will recursively invoke themselves with the next <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②③">any</a></code> in <var>queue</var>.</p>
+   processing steps will recursively invoke themselves with the next <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⑤">any</a></code> in <var>queue</var>.</p>
                <p>If no such value <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#list-contain" id="ref-for-list-contain">exists</a>, then the processing steps will terminate, <b>unsetting</b> <var>activeInnerSubscription</var>, so that future values emitted from <var>sourceObservable</var> are processed correctly.</p>
               </div>
             </ol>
@@ -1687,7 +1688,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
           </ol>
         </dl>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑤">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑧">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①⓪">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑦">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑧">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①⓪">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable①①">Subscribe</a> to <var>sourceObservable</var> given <var>sourceObserver</var> and <var>options</var>.</p>
       </ol>
@@ -1696,7 +1697,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
     </ol>
    </div>
    <div class="algorithm" data-algorithm="flatmap process next value steps">
-     The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="flatmap-process-next-value-steps">flatmap process next value steps</dfn>, given an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②④">any</a></code> <var>value</var>, a <code class="idl"><a data-link-type="idl" href="#subscriber" id="ref-for-subscriber②⓪">Subscriber</a></code> <var>subscriber</var>, a <code class="idl"><a data-link-type="idl" href="#callbackdef-mapper" id="ref-for-callbackdef-mapper③">Mapper</a></code> <var>mapper</var>, and <b>references</b> to all of the following: a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#list" id="ref-for-list②">list</a> of <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⑤">any</a></code> values <var>queue</var>, a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean②">boolean</a> <var>activeInnerSubscription</var>, a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean③">boolean</a> <var>outerSubscriptionHasCompleted</var>, and an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long⑧">unsigned long long</a></code> <var>idx</var>: 
+     The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="flatmap-process-next-value-steps">flatmap process next value steps</dfn>, given an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⑥">any</a></code> <var>value</var>, a <code class="idl"><a data-link-type="idl" href="#subscriber" id="ref-for-subscriber②⓪">Subscriber</a></code> <var>subscriber</var>, a <code class="idl"><a data-link-type="idl" href="#callbackdef-mapper" id="ref-for-callbackdef-mapper③">Mapper</a></code> <var>mapper</var>, and <b>references</b> to all of the following: a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#list" id="ref-for-list②">list</a> of <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⑦">any</a></code> values <var>queue</var>, a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean②">boolean</a> <var>activeInnerSubscription</var>, a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean③">boolean</a> <var>outerSubscriptionHasCompleted</var>, and an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long⑧">unsigned long long</a></code> <var>idx</var>: 
     <ol>
      <li data-md>
       <p>Let <var>mappedResult</var> be the result of <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function①①">invoking</a> <var>mapper</var> with <var>value</var> and <var>idx</var>.</p>
@@ -1747,7 +1748,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
         </ol>
       </dl>
      <li data-md>
-      <p>Let <var>innerOptions</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑥">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑨">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①①">signal</a>.</p>
+      <p>Let <var>innerOptions</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑧">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑨">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①①">signal</a>.</p>
      <li data-md>
       <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable①②">Subscribe</a> to <var>innerObservable</var> given <var>innerObserver</var> and <var>innerOptions</var>.</p>
     </ol>
@@ -1814,7 +1815,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
           </ol>
         </dl>
        <li data-md>
-        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑦">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①⓪">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①②">signal</a>.</p>
+        <p>Let <var>options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑨">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①⓪">signal</a></code> is <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①②">signal</a>.</p>
        <li data-md>
         <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable①③">Subscribe</a> to <var>sourceObservable</var> given <var>sourceObserver</var> and <var>options</var>.</p>
       </ol>
@@ -1823,7 +1824,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
     </ol>
    </div>
    <div class="algorithm" data-algorithm="switchmap process next value steps">
-     The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="switchmap-process-next-value-steps">switchmap process next value steps</dfn>, given an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⑥">any</a></code> <var>value</var>, a <code class="idl"><a data-link-type="idl" href="#subscriber" id="ref-for-subscriber②②">Subscriber</a></code> <var>subscriber</var>, a <code class="idl"><a data-link-type="idl" href="#callbackdef-mapper" id="ref-for-callbackdef-mapper④">Mapper</a></code> <var>mapper</var>, and <b>references</b> to all of the following: an <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑤">AbortController</a></code> <var>activeInnerAbortController</var>, a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean⑤">boolean</a> <var>outerSubscriptionHasCompleted</var>, and an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long①⓪">unsigned long long</a></code> <var>idx</var> are to run these steps: 
+     The <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="switchmap-process-next-value-steps">switchmap process next value steps</dfn>, given an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-any" id="ref-for-idl-any②⑧">any</a></code> <var>value</var>, a <code class="idl"><a data-link-type="idl" href="#subscriber" id="ref-for-subscriber②②">Subscriber</a></code> <var>subscriber</var>, a <code class="idl"><a data-link-type="idl" href="#callbackdef-mapper" id="ref-for-callbackdef-mapper④">Mapper</a></code> <var>mapper</var>, and <b>references</b> to all of the following: an <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑤">AbortController</a></code> <var>activeInnerAbortController</var>, a <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#boolean" id="ref-for-boolean⑤">boolean</a> <var>outerSubscriptionHasCompleted</var>, and an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long①⓪">unsigned long long</a></code> <var>idx</var> are to run these steps: 
     <ol>
      <li data-md>
       <p>Let <var>mappedResult</var> be the result of <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function①②">invoking</a> <var>mapper</var> with <var>value</var> and <var>idx</var>.</p>
@@ -1858,7 +1859,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
         </ol>
       </dl>
      <li data-md>
-      <p>Let <var>innerOptions</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑧">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①①">signal</a></code> is the
+      <p>Let <var>innerOptions</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②⓪">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①①">signal</a></code> is the
   result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal②">creating a dependent abort signal</a> from the list
   «<var>activeInnerAbortController</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal②">signal</a>, <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①③">signal</a>», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal④">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm①">current realm</a>.</p>
      <li data-md>
@@ -1872,7 +1873,7 @@ <h4 class="heading settled" data-level="2.3.2" id="observable-returning-operator
       <p><span class="XXX">TODO: Spec this and use <var>callback</var>.</span></p>
     </ol>
    </div>
-   <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators"><span class="secno">2.3.3. </span><span class="content"><code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise⑥">Promise</a></code>-returning operators</span><a class="self-link" href="#promise-returning-operators"></a></h4>
+   <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators"><span class="secno">2.3.3. </span><span class="content"><code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise⑧">Promise</a></code>-returning operators</span><a class="self-link" href="#promise-returning-operators"></a></h4>
    <div class="algorithm" data-algorithm="toArray(options)" data-algorithm-for="Observable">
      The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="toArray(options)|toArray()" id="dom-observable-toarray"><code>toArray(<var>options</var>)</code></dfn> method steps are: 
     <ol>
@@ -1934,7 +1935,7 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
      <li data-md>
       <p>Let <var>visitor callback controller</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new⑨">new</a> <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑥">AbortController</a></code>.</p>
      <li data-md>
-      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions①⑨">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①⑧">signal</a></code> is the
+      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②①">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①⑧">signal</a></code> is the
  result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal③">creating a dependent abort signal</a> from the list
  «<var>visitor callback controller</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal③">signal</a>, <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal①⑨">signal</a></code> if non-null», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑤">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm②">current realm</a>.</p>
       <div class="note" role="note">
@@ -1944,7 +1945,7 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
    version of the given value along the chain.</p>
        <p>For this operator, however, the below <var>observer</var>’s <a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps①⑥">next steps</a> are
    responsible for actually aborting the underlying subscription to <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③⓪">this</a>, in the event
-   that <var>callback</var> throws an exception. In that case, the <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②⓪">SubscribeOptions</a></code>'s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②⓪">signal</a></code> we pass through to "<a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable①⑦">Subscribe to an <code>Observable</code></a>", needs to be a <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal④">dependent signal</a> derived from <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②①">signal</a></code>, <strong>and</strong> the <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑥">AbortSignal</a></code> of an <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑦">AbortController</a></code> that the <a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps①⑦">next steps</a> below has access to, and can <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort③">signal
+   that <var>callback</var> throws an exception. In that case, the <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②②">SubscribeOptions</a></code>'s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②⓪">signal</a></code> we pass through to "<a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable①⑦">Subscribe to an <code>Observable</code></a>", needs to be a <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal④">dependent signal</a> derived from <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②①">signal</a></code>, <strong>and</strong> the <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑥">AbortSignal</a></code> of an <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑦">AbortController</a></code> that the <a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps①⑦">next steps</a> below has access to, and can <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort③">signal
    abort</a> when needed. </p>
       </div>
      <li data-md>
@@ -2007,7 +2008,7 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
      <li data-md>
       <p>Let <var>controller</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①⓪">new</a> <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑧">AbortController</a></code>.</p>
      <li data-md>
-      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②①">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②⑨">signal</a></code> is the
+      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②③">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal②⑨">signal</a></code> is the
  result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal⑤">creating a dependent abort signal</a> from the list
  «<var>controller</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal④">signal</a>, <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③⓪">signal</a></code> if non-null», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑦">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm③">current realm</a>.</p>
      <li data-md>
@@ -2055,17 +2056,16 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
       <p>Return <var>p</var>.</p>
     </ol>
    </div>
-   <div class="algorithm" data-algorithm="find(predicate, options)" data-algorithm-for="Observable">
-     The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="find(predicate, options)|find(predicate)" id="dom-observable-find"><code>find(<var>predicate</var>, <var>options</var>)</code></dfn> method steps are: 
+   <div class="algorithm" data-algorithm="first(options)" data-algorithm-for="Observable">
+     The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="first(options)|first()" id="dom-observable-first"><code>first(<var>options</var>)</code></dfn> method steps are: 
     <ol>
      <li data-md>
       <p>Let <var>p</var> <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#a-new-promise" id="ref-for-a-new-promise③">a new promise</a>.</p>
      <li data-md>
       <p>Let <var>controller</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①①">new</a> <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller⑨">AbortController</a></code>.</p>
      <li data-md>
-      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②②">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③⑤">signal</a></code> is the
- result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal⑥">creating a dependent abort signal</a> from the list
- «<var>controller</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal⑤">signal</a>, <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③⑥">signal</a></code> if non-null», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑧">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm④">current realm</a>.</p>
+      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②④">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③⑤">signal</a></code> is the
+ result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal⑥">creating a dependent abort signal</a> from the list «<var>controller</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal⑤">signal</a>, <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③⑥">signal</a></code> if non-null», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑧">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm④">current realm</a>.</p>
      <li data-md>
       <p>If <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal③⑦">signal</a></code> is <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted⑤">aborted</a>, then:</p>
       <ol>
@@ -2082,52 +2082,60 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
   reason</a>.</p>
       </ol>
      <li data-md>
-      <p>Let <var>idx</var> be an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long①③">unsigned long long</a></code>, initially 0.</p>
-     <li data-md>
-      <p>Let <var>observer</var> be a new <a data-link-type="dfn" href="#internal-observer" id="ref-for-internal-observer①⑧">internal observer</a>, initialized as follows:</p>
+      <p>Let <var>internal observer</var> be a new <a data-link-type="dfn" href="#internal-observer" id="ref-for-internal-observer①⑧">internal observer</a>, initialized as follows:</p>
       <dl>
        <dt data-md><a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps②⓪">next steps</a>
        <dd data-md>
         <ol>
          <li data-md>
-          <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function①⑤">Invoke</a> <var>predicate</var> with the passed in <var>value</var> an <var>idx</var>, and let <var>passed</var> be the
-   returned value.</p>
-          <p>If <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#an-exception-was-thrown" id="ref-for-an-exception-was-thrown①⑧">an exception <var>E</var> was thrown</a>, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①④">reject</a> <var>p</var> with <var>E</var>, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort⑦">signal abort</a> <var>controller</var> with <var>E</var>.</p>
-         <li data-md>
-          <p>Set <var>idx</var> to <var>idx</var> + 1.</p>
-         <li data-md>
-          <p>If <var>passed</var> is true, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve④">resolve</a> <var>p</var> with <var>value</var>, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort⑧">signal
-  abort</a> <var>controller</var>.</p>
+          <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve④">Resolve</a> <var>p</var> with the passed in <var>value</var>.</p>
+          <ol>
+           <li data-md>
+            <p><a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort⑦">Signal abort</a> <var>controller</var>.</p>
+          </ol>
         </ol>
        <dt data-md><a data-link-type="dfn" href="#internal-observer-error-steps" id="ref-for-internal-observer-error-steps①⑧">error steps</a>
        <dd data-md>
-        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑤">Reject</a> <var>p</var> with the passed in <var>error</var>.</p>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①④">Reject</a> <var>p</var> with the passed in <var>error</var>.</p>
        <dt data-md><a data-link-type="dfn" href="#internal-observer-complete-steps" id="ref-for-internal-observer-complete-steps①⑦">complete steps</a>
        <dd data-md>
         <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑤">Resolve</a> <var>p</var> with <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-undefined" id="ref-for-idl-undefined①⓪">undefined</a></code>.</p>
+        <p class="note" role="note"><span class="marker">Note:</span> This is only reached when the source <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④③">Observable</a></code> completes <em>before</em> it emits a
+  single value; in this case, resolving with <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-undefined" id="ref-for-idl-undefined①①">undefined</a></code> is harmless but makes it
+  difficult to distinguish between the first value trule being <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-undefined" id="ref-for-idl-undefined①②">undefined</a></code> and premature
+  completion. See <a href="https://github.com/WICG/observable/issues/132">#132</a> for
+  discussion on this.</p>
       </dl>
      <li data-md>
-      <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable②⓪">Subscribe</a> to <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③③">this</a> given <var>observer</var> and <var>internal options</var>.</p>
+      <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable②⓪">Subscribe</a> to <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③③">this</a> given <var>internal
+ observer</var> and <var>internal options</var>.</p>
      <li data-md>
       <p>Return <var>p</var>.</p>
     </ol>
    </div>
-   <div class="algorithm" data-algorithm="some(predicate, options)" data-algorithm-for="Observable">
-     The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="some(predicate, options)|some(predicate)" id="dom-observable-some"><code>some(<var>predicate</var>, <var>options</var>)</code></dfn> method steps are: 
+   <div class="algorithm" data-algorithm="last(options)" data-algorithm-for="Observable">
+     The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="last(options)|last()" id="dom-observable-last"><code>last(<var>options</var>)</code></dfn> method steps are: 
+    <ol>
+     <li data-md>
+      <p><span class="XXX">TODO: Spec this and use <var>options</var>.</span></p>
+    </ol>
+   </div>
+   <div class="algorithm" data-algorithm="find(predicate, options)" data-algorithm-for="Observable">
+     The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="find(predicate, options)|find(predicate)" id="dom-observable-find"><code>find(<var>predicate</var>, <var>options</var>)</code></dfn> method steps are: 
     <ol>
      <li data-md>
       <p>Let <var>p</var> <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#a-new-promise" id="ref-for-a-new-promise④">a new promise</a>.</p>
      <li data-md>
       <p>Let <var>controller</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①②">new</a> <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller①⓪">AbortController</a></code>.</p>
      <li data-md>
-      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②③">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④①">signal</a></code> is the
+      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②⑤">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④①">signal</a></code> is the
  result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal⑦">creating a dependent abort signal</a> from the list
  «<var>controller</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal⑥">signal</a>, <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④②">signal</a></code> if non-null», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal⑨">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm⑤">current realm</a>.</p>
      <li data-md>
       <p>If <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④③">signal</a></code> is <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted⑥">aborted</a>, then:</p>
       <ol>
        <li data-md>
-        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑥">Reject</a> <var>p</var> with <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④④">signal</a></code>'s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-abort-reason" id="ref-for-abortsignal-abort-reason⑧">abort reason</a>.</p>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑤">Reject</a> <var>p</var> with <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④④">signal</a></code>'s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-abort-reason" id="ref-for-abortsignal-abort-reason⑧">abort reason</a>.</p>
        <li data-md>
         <p>Return <var>p</var>.</p>
       </ol>
@@ -2135,11 +2143,11 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
       <p><a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-add" id="ref-for-abortsignal-add⑤">Add the following abort algorithm</a> to <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④⑤">signal</a></code>:</p>
       <ol>
        <li data-md>
-        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑦">Reject</a> <var>p</var> with <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④⑥">signal</a></code>'s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-abort-reason" id="ref-for-abortsignal-abort-reason⑨">abort
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑥">Reject</a> <var>p</var> with <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④⑥">signal</a></code>'s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-abort-reason" id="ref-for-abortsignal-abort-reason⑨">abort
   reason</a>.</p>
       </ol>
      <li data-md>
-      <p>Let <var>idx</var> be an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long①④">unsigned long long</a></code>, initially 0.</p>
+      <p>Let <var>idx</var> be an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long①③">unsigned long long</a></code>, initially 0.</p>
      <li data-md>
       <p>Let <var>observer</var> be a new <a data-link-type="dfn" href="#internal-observer" id="ref-for-internal-observer①⑨">internal observer</a>, initialized as follows:</p>
       <dl>
@@ -2147,20 +2155,21 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
        <dd data-md>
         <ol>
          <li data-md>
-          <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function①⑥">Invoke</a> <var>predicate</var> with the passed in <var>value</var> and <var>idx</var>, and let <var>passed</var> be the returned value.</p>
-          <p>If <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#an-exception-was-thrown" id="ref-for-an-exception-was-thrown①⑨">an exception <var>E</var> was thrown</a>, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑧">reject</a> <var>p</var> with <var>E</var>, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort⑨">signal abort</a> <var>controller</var> with <var>E</var>.</p>
+          <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function①⑤">Invoke</a> <var>predicate</var> with the passed in <var>value</var> an <var>idx</var>, and let <var>passed</var> be the
+   returned value.</p>
+          <p>If <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#an-exception-was-thrown" id="ref-for-an-exception-was-thrown①⑧">an exception <var>E</var> was thrown</a>, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑦">reject</a> <var>p</var> with <var>E</var>, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort⑧">signal abort</a> <var>controller</var> with <var>E</var>.</p>
          <li data-md>
           <p>Set <var>idx</var> to <var>idx</var> + 1.</p>
          <li data-md>
-          <p>If <var>passed</var> is true, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑥">resolve</a> <var>p</var> with true, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort①⓪">signal
+          <p>If <var>passed</var> is true, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑥">resolve</a> <var>p</var> with <var>value</var>, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort⑨">signal
   abort</a> <var>controller</var>.</p>
         </ol>
        <dt data-md><a data-link-type="dfn" href="#internal-observer-error-steps" id="ref-for-internal-observer-error-steps①⑨">error steps</a>
        <dd data-md>
-        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑨">Reject</a> <var>p</var> with the passed in <var>error</var>.</p>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑧">Reject</a> <var>p</var> with the passed in <var>error</var>.</p>
        <dt data-md><a data-link-type="dfn" href="#internal-observer-complete-steps" id="ref-for-internal-observer-complete-steps①⑧">complete steps</a>
        <dd data-md>
-        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑦">Resolve</a> <var>p</var> with false.</p>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑦">Resolve</a> <var>p</var> with <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-undefined" id="ref-for-idl-undefined①③">undefined</a></code>.</p>
       </dl>
      <li data-md>
       <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable②①">Subscribe</a> to <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③④">this</a> given <var>observer</var> and <var>internal options</var>.</p>
@@ -2168,6 +2177,62 @@ <h4 class="heading settled" data-level="2.3.3" id="promise-returning-operators">
       <p>Return <var>p</var>.</p>
     </ol>
    </div>
+   <div class="algorithm" data-algorithm="some(predicate, options)" data-algorithm-for="Observable">
+     The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="some(predicate, options)|some(predicate)" id="dom-observable-some"><code>some(<var>predicate</var>, <var>options</var>)</code></dfn> method steps are: 
+    <ol>
+     <li data-md>
+      <p>Let <var>p</var> <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#a-new-promise" id="ref-for-a-new-promise⑤">a new promise</a>.</p>
+     <li data-md>
+      <p>Let <var>controller</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①③">new</a> <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortcontroller" id="ref-for-abortcontroller①①">AbortController</a></code>.</p>
+     <li data-md>
+      <p>Let <var>internal options</var> be a new <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②⑥">SubscribeOptions</a></code> whose <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④⑦">signal</a></code> is the
+ result of <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#create-a-dependent-abort-signal" id="ref-for-create-a-dependent-abort-signal⑧">creating a dependent abort signal</a> from the list
+ «<var>controller</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal" id="ref-for-abortcontroller-signal⑦">signal</a>, <var>options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④⑧">signal</a></code> if non-null», using <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal①⓪">AbortSignal</a></code>, and the <a data-link-type="dfn" href="https://tc39.es/ecma262/#current-realm" id="ref-for-current-realm⑥">current realm</a>.</p>
+     <li data-md>
+      <p>If <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal④⑨">signal</a></code> is <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted⑦">aborted</a>, then:</p>
+      <ol>
+       <li data-md>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject①⑨">Reject</a> <var>p</var> with <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑤⓪">signal</a></code>'s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-abort-reason" id="ref-for-abortsignal-abort-reason①⓪">abort reason</a>.</p>
+       <li data-md>
+        <p>Return <var>p</var>.</p>
+      </ol>
+     <li data-md>
+      <p><a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-add" id="ref-for-abortsignal-add⑥">Add the following abort algorithm</a> to <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑤①">signal</a></code>:</p>
+      <ol>
+       <li data-md>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject②⓪">Reject</a> <var>p</var> with <var>internal options</var>’s <code class="idl"><a data-link-type="idl" href="#dom-subscribeoptions-signal" id="ref-for-dom-subscribeoptions-signal⑤②">signal</a></code>'s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-abort-reason" id="ref-for-abortsignal-abort-reason①①">abort
+  reason</a>.</p>
+      </ol>
+     <li data-md>
+      <p>Let <var>idx</var> be an <code class="idl"><a data-link-type="idl" href="https://webidl.spec.whatwg.org/#idl-unsigned-long-long" id="ref-for-idl-unsigned-long-long①④">unsigned long long</a></code>, initially 0.</p>
+     <li data-md>
+      <p>Let <var>observer</var> be a new <a data-link-type="dfn" href="#internal-observer" id="ref-for-internal-observer②⓪">internal observer</a>, initialized as follows:</p>
+      <dl>
+       <dt data-md><a data-link-type="dfn" href="#internal-observer-next-steps" id="ref-for-internal-observer-next-steps②②">next steps</a>
+       <dd data-md>
+        <ol>
+         <li data-md>
+          <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#invoke-a-callback-function" id="ref-for-invoke-a-callback-function①⑥">Invoke</a> <var>predicate</var> with the passed in <var>value</var> and <var>idx</var>, and let <var>passed</var> be the returned value.</p>
+          <p>If <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#an-exception-was-thrown" id="ref-for-an-exception-was-thrown①⑨">an exception <var>E</var> was thrown</a>, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject②①">reject</a> <var>p</var> with <var>E</var>, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort①⓪">signal abort</a> <var>controller</var> with <var>E</var>.</p>
+         <li data-md>
+          <p>Set <var>idx</var> to <var>idx</var> + 1.</p>
+         <li data-md>
+          <p>If <var>passed</var> is true, then <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑧">resolve</a> <var>p</var> with true, and <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortcontroller-signal-abort" id="ref-for-abortcontroller-signal-abort①①">signal
+  abort</a> <var>controller</var>.</p>
+        </ol>
+       <dt data-md><a data-link-type="dfn" href="#internal-observer-error-steps" id="ref-for-internal-observer-error-steps②⓪">error steps</a>
+       <dd data-md>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject②②">Reject</a> <var>p</var> with the passed in <var>error</var>.</p>
+       <dt data-md><a data-link-type="dfn" href="#internal-observer-complete-steps" id="ref-for-internal-observer-complete-steps①⑨">complete steps</a>
+       <dd data-md>
+        <p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve⑨">Resolve</a> <var>p</var> with false.</p>
+      </dl>
+     <li data-md>
+      <p><a data-link-type="dfn" href="#observable-subscribe-to-an-observable" id="ref-for-observable-subscribe-to-an-observable②②">Subscribe</a> to <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③⑤">this</a> given <var>observer</var> and <var>internal options</var>.</p>
+     <li data-md>
+      <p>Return <var>p</var>.</p>
+    </ol>
+   </div>
    <div class="algorithm" data-algorithm="reduce(reducer, initialValue, options)" data-algorithm-for="Observable">
      The <dfn class="dfn-paneled idl-code" data-dfn-for="Observable" data-dfn-type="method" data-export data-lt="reduce(reducer, initialValue, options)|reduce(reducer, initialValue)|reduce(reducer)" id="dom-observable-reduce"><code>reduce(<var>reducer</var>, <var>initialValue</var>, <var>options</var>)</code></dfn> method steps are: 
     <ol>
@@ -2182,19 +2247,19 @@ <h2 class="heading settled" data-level="3" id="event-target-integration"><span c
 };
 
 <c- b>partial</c-> <c- b>interface</c-> <a class="idl-code" data-link-type="interface" href="https://dom.spec.whatwg.org/#eventtarget" id="ref-for-eventtarget①"><c- g>EventTarget</c-></a> {
-  <a data-link-type="idl-name" href="#observable" id="ref-for-observable④③"><c- n>Observable</c-></a> <a class="idl-code" data-link-type="method" href="#dom-eventtarget-on" id="ref-for-dom-eventtarget-on①"><c- g>on</c-></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="EventTarget/on(type, options), EventTarget/on(type)" data-dfn-type="argument" data-export id="dom-eventtarget-on-type-options-type"><code><c- g>type</c-></code><a class="self-link" href="#dom-eventtarget-on-type-options-type"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-observableeventlisteneroptions" id="ref-for-dictdef-observableeventlisteneroptions"><c- n>ObservableEventListenerOptions</c-></a> <dfn class="idl-code" data-dfn-for="EventTarget/on(type, options), EventTarget/on(type)" data-dfn-type="argument" data-export id="dom-eventtarget-on-type-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-eventtarget-on-type-options-options"></a></dfn> = {});
+  <a data-link-type="idl-name" href="#observable" id="ref-for-observable④④"><c- n>Observable</c-></a> <a class="idl-code" data-link-type="method" href="#dom-eventtarget-on" id="ref-for-dom-eventtarget-on①"><c- g>on</c-></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="EventTarget/on(type, options), EventTarget/on(type)" data-dfn-type="argument" data-export id="dom-eventtarget-on-type-options-type"><code><c- g>type</c-></code><a class="self-link" href="#dom-eventtarget-on-type-options-type"></a></dfn>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-observableeventlisteneroptions" id="ref-for-dictdef-observableeventlisteneroptions"><c- n>ObservableEventListenerOptions</c-></a> <dfn class="idl-code" data-dfn-for="EventTarget/on(type, options), EventTarget/on(type)" data-dfn-type="argument" data-export id="dom-eventtarget-on-type-options-options"><code><c- g>options</c-></code><a class="self-link" href="#dom-eventtarget-on-type-options-options"></a></dfn> = {});
 };
 </pre>
    <div class="algorithm" data-algorithm="on(type, options)" data-algorithm-for="EventTarget">
      The <dfn class="dfn-paneled idl-code" data-dfn-for="EventTarget" data-dfn-type="method" data-export data-lt="on(type, options)|on(type)" id="dom-eventtarget-on"><code>on(<var>type</var>, <var>options</var>)</code></dfn> method steps are: 
     <ol>
      <li data-md>
-      <p>If <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③⑤">this</a>'s <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/webappapis.html#concept-relevant-global" id="ref-for-concept-relevant-global⑥">relevant global object</a> is a <code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/nav-history-apis.html#window" id="ref-for-window⑥">Window</a></code> object, and its <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/nav-history-apis.html#concept-document-window" id="ref-for-concept-document-window⑥">associated
+      <p>If <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③⑥">this</a>'s <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/webappapis.html#concept-relevant-global" id="ref-for-concept-relevant-global⑥">relevant global object</a> is a <code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/nav-history-apis.html#window" id="ref-for-window⑥">Window</a></code> object, and its <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/nav-history-apis.html#concept-document-window" id="ref-for-concept-document-window⑥">associated
  Document</a> is not <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/document-sequences.html#fully-active" id="ref-for-fully-active⑥">fully active</a>, then return.</p>
      <li data-md>
-      <p>Let <var>event target</var> be <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③⑥">this</a>.</p>
+      <p>Let <var>event target</var> be <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#this" id="ref-for-this③⑦">this</a>.</p>
      <li data-md>
-      <p>Let <var>observable</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①③">new</a> <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④④">Observable</a></code>, initialized as follows:</p>
+      <p>Let <var>observable</var> be a <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#new" id="ref-for-new①④">new</a> <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④⑤">Observable</a></code>, initialized as follows:</p>
       <dl>
        <dt data-md><a data-link-type="dfn" href="#observable-subscribe-callback" id="ref-for-observable-subscribe-callback①②">subscribe callback</a>
        <dd data-md>
@@ -2205,7 +2270,7 @@ <h2 class="heading settled" data-level="3" id="event-target-integration"><span c
           <p class="note" role="note"><span class="marker">Note:</span> This is meant to capture the fact that <var>event target</var> can be garbage collected
  by the time this algorithm runs upon subscription.</p>
          <li data-md>
-          <p>If <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①⑤">signal</a> is <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted⑦">aborted</a>, abort these
+          <p>If <var>subscriber</var>’s <a data-link-type="dfn" href="#subscriber-signal" id="ref-for-subscriber-signal①⑤">signal</a> is <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#abortsignal-aborted" id="ref-for-abortsignal-aborted⑧">aborted</a>, abort these
  steps.</p>
          <li data-md>
           <p><a data-link-type="dfn" href="https://dom.spec.whatwg.org/#add-an-event-listener" id="ref-for-add-an-event-listener">Add an event listener</a> with <var>event target</var> and an <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#concept-event-listener" id="ref-for-concept-event-listener">event listener</a> defined as follows:</p>
@@ -2230,7 +2295,7 @@ <h2 class="heading settled" data-level="3" id="event-target-integration"><span c
            <dt data-md><a data-link-type="dfn" href="https://dom.spec.whatwg.org#event-listener-signal" id="ref-for-event-listener-signal">signal</a>
            <dd data-md>
             <p>null</p>
-            <p class="note" role="note"><span class="marker">Note:</span> The <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal①⓪">AbortSignal</a></code> for event listeners <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#add-an-event-listener" id="ref-for-add-an-event-listener①">added</a> by <code class="idl"><a data-link-type="idl" href="#dom-eventtarget-on" id="ref-for-dom-eventtarget-on②">on()</a></code> is managed by the <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④⑤">Observable</a></code> itself. See <code class="idl"><a data-link-type="idl" href="#dom-observable-subscribe" id="ref-for-dom-observable-subscribe⑤">subscribe()</a></code> and <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②④">SubscribeOptions</a></code>.</p>
+            <p class="note" role="note"><span class="marker">Note:</span> The <code class="idl"><a data-link-type="idl" href="https://dom.spec.whatwg.org/#abortsignal" id="ref-for-abortsignal①①">AbortSignal</a></code> for event listeners <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#add-an-event-listener" id="ref-for-add-an-event-listener①">added</a> by <code class="idl"><a data-link-type="idl" href="#dom-eventtarget-on" id="ref-for-dom-eventtarget-on②">on()</a></code> is managed by the <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④⑥">Observable</a></code> itself. See <code class="idl"><a data-link-type="idl" href="#dom-observable-subscribe" id="ref-for-dom-observable-subscribe⑤">subscribe()</a></code> and <code class="idl"><a data-link-type="idl" href="#dictdef-subscribeoptions" id="ref-for-dictdef-subscribeoptions②⑦">SubscribeOptions</a></code>.</p>
           </dl>
         </ol>
       </dl>
@@ -2262,7 +2327,7 @@ <h2 class="heading settled" data-level="4" id="security-and-privacy"><span class
    </ul>
    <h2 class="heading settled" data-level="5" id="acks"><span class="secno">5. </span><span class="content">Acknowledgements</span><a class="self-link" href="#acks"></a></h2>
    <p>A special thanks to <a href="https://benlesh.com/">Ben Lesh</a> for much of the design
-input for the <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④⑥">Observable</a></code> API, and his many years of work maintaining
+input for the <code class="idl"><a data-link-type="idl" href="#observable" id="ref-for-observable④⑦">Observable</a></code> API, and his many years of work maintaining
 userland Observable code that made this contribution to the web platform
 possible.</p>
   </main>
@@ -2297,12 +2362,16 @@ <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="c
    <li><a href="#dom-observable-finally">finally(callback)</a><span>, in § 2.3.2</span>
    <li><a href="#dom-observable-find">find(predicate)</a><span>, in § 2.3.3</span>
    <li><a href="#dom-observable-find">find(predicate, options)</a><span>, in § 2.3.3</span>
+   <li><a href="#dom-observable-first">first()</a><span>, in § 2.3.3</span>
+   <li><a href="#dom-observable-first">first(options)</a><span>, in § 2.3.3</span>
    <li><a href="#dom-observable-flatmap">flatMap(mapper)</a><span>, in § 2.3.2</span>
    <li><a href="#flatmap-process-next-value-steps">flatmap process next value steps</a><span>, in § 2.3.2</span>
    <li><a href="#dom-observable-foreach">forEach(callback)</a><span>, in § 2.3.3</span>
    <li><a href="#dom-observable-foreach">forEach(callback, options)</a><span>, in § 2.3.3</span>
    <li><a href="#dom-observable-from">from(value)</a><span>, in § 2.2</span>
    <li><a href="#internal-observer">internal observer</a><span>, in § 2.2.1</span>
+   <li><a href="#dom-observable-last">last()</a><span>, in § 2.3.3</span>
+   <li><a href="#dom-observable-last">last(options)</a><span>, in § 2.3.3</span>
    <li><a href="#dom-observable-map">map(mapper)</a><span>, in § 2.3.2</span>
    <li><a href="#callbackdef-mapper">Mapper</a><span>, in § 2.2</span>
    <li><a href="#dom-subscriptionobserver-next">next</a><span>, in § 2.2</span>
@@ -2513,7 +2582,8 @@ <h2 class="no-num no-ref heading settled" id="idl-index"><span class="content">I
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#idl-sequence"><c- b>sequence</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any"><c- b>any</c-></a>>> <a class="idl-code" data-link-type="method" href="#dom-observable-toarray"><c- g>toArray</c-></a>(<c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-toarray-options-options"><code><c- g>options</c-></code></a> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-undefined"><c- b>undefined</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-foreach"><c- g>forEach</c-></a>(<a data-link-type="idl-name" href="#callbackdef-visitor"><c- n>Visitor</c-></a> <a href="#dom-observable-foreach-callback-options-callback"><code><c- g>callback</c-></code></a>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-foreach-callback-options-options"><code><c- g>options</c-></code></a> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-boolean"><c- b>boolean</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-every"><c- g>every</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate"><c- n>Predicate</c-></a> <a href="#dom-observable-every-predicate-options-predicate"><code><c- g>predicate</c-></code></a>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-every-predicate-options-options"><code><c- g>options</c-></code></a> = {});
-  // Maybe? Promise&lt;any> first(optional SubscribeOptions options = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-first"><c- g>first</c-></a>(<c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-first-options-options"><code><c- g>options</c-></code></a> = {});
+  <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-last"><c- g>last</c-></a>(<c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-last-options-options"><code><c- g>options</c-></code></a> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-find"><c- g>find</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate"><c- n>Predicate</c-></a> <a href="#dom-observable-find-predicate-options-predicate"><code><c- g>predicate</c-></code></a>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-find-predicate-options-options"><code><c- g>options</c-></code></a> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-boolean"><c- b>boolean</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-some"><c- g>some</c-></a>(<a data-link-type="idl-name" href="#callbackdef-predicate"><c- n>Predicate</c-></a> <a href="#dom-observable-some-predicate-options-predicate"><code><c- g>predicate</c-></code></a>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-some-predicate-options-options"><code><c- g>options</c-></code></a> = {});
   <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any"><c- b>any</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-observable-reduce"><c- g>reduce</c-></a>(<a data-link-type="idl-name" href="#callbackdef-reducer"><c- n>Reducer</c-></a> <a href="#dom-observable-reduce-reducer-initialvalue-options-reducer"><code><c- g>reducer</c-></code></a>, <c- b>optional</c-> <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-any"><c- b>any</c-></a> <a href="#dom-observable-reduce-reducer-initialvalue-options-initialvalue"><code><c- g>initialValue</c-></code></a>, <c- b>optional</c-> <a data-link-type="idl-name" href="#dictdef-subscribeoptions"><c- n>SubscribeOptions</c-></a> <a href="#dom-observable-reduce-reducer-initialvalue-options-options"><code><c- g>options</c-></code></a> = {});
@@ -2843,30 +2913,30 @@ <h2 class="no-num no-ref heading settled" id="issues-index"><span class="content
 </script>
 <script>/* Boilerplate: script-dfn-panel-json */
 window.dfnpanelData = {};
-window.dfnpanelData['2e66eaf1'] = {"dfnID": "2e66eaf1", "url": "https://dom.spec.whatwg.org/#abortcontroller", "dfnText": "AbortController", "refSections": [{"refs": [{"id": "ref-for-abortcontroller"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortcontroller\u2460"}, {"id": "ref-for-abortcontroller\u2461"}, {"id": "ref-for-abortcontroller\u2462"}, {"id": "ref-for-abortcontroller\u2463"}, {"id": "ref-for-abortcontroller\u2464"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortcontroller\u2465"}, {"id": "ref-for-abortcontroller\u2466"}, {"id": "ref-for-abortcontroller\u2467"}, {"id": "ref-for-abortcontroller\u2468"}, {"id": "ref-for-abortcontroller\u2460\u24ea"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
-window.dfnpanelData['cca3cdb2'] = {"dfnID": "cca3cdb2", "url": "https://dom.spec.whatwg.org/#abortsignal", "dfnText": "AbortSignal", "refSections": [{"refs": [{"id": "ref-for-abortsignal"}, {"id": "ref-for-abortsignal\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortsignal\u2461"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-abortsignal\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortsignal\u2463"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortsignal\u2464"}, {"id": "ref-for-abortsignal\u2465"}, {"id": "ref-for-abortsignal\u2466"}, {"id": "ref-for-abortsignal\u2467"}, {"id": "ref-for-abortsignal\u2468"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-abortsignal\u2460\u24ea"}], "title": "3. EventTarget integration"}], "external": true};
+window.dfnpanelData['2e66eaf1'] = {"dfnID": "2e66eaf1", "url": "https://dom.spec.whatwg.org/#abortcontroller", "dfnText": "AbortController", "refSections": [{"refs": [{"id": "ref-for-abortcontroller"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortcontroller\u2460"}, {"id": "ref-for-abortcontroller\u2461"}, {"id": "ref-for-abortcontroller\u2462"}, {"id": "ref-for-abortcontroller\u2463"}, {"id": "ref-for-abortcontroller\u2464"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortcontroller\u2465"}, {"id": "ref-for-abortcontroller\u2466"}, {"id": "ref-for-abortcontroller\u2467"}, {"id": "ref-for-abortcontroller\u2468"}, {"id": "ref-for-abortcontroller\u2460\u24ea"}, {"id": "ref-for-abortcontroller\u2460\u2460"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['cca3cdb2'] = {"dfnID": "cca3cdb2", "url": "https://dom.spec.whatwg.org/#abortsignal", "dfnText": "AbortSignal", "refSections": [{"refs": [{"id": "ref-for-abortsignal"}, {"id": "ref-for-abortsignal\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortsignal\u2461"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-abortsignal\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortsignal\u2463"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortsignal\u2464"}, {"id": "ref-for-abortsignal\u2465"}, {"id": "ref-for-abortsignal\u2466"}, {"id": "ref-for-abortsignal\u2467"}, {"id": "ref-for-abortsignal\u2468"}, {"id": "ref-for-abortsignal\u2460\u24ea"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-abortsignal\u2460\u2460"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['85394472'] = {"dfnID": "85394472", "url": "https://dom.spec.whatwg.org/#document", "dfnText": "Document", "refSections": [{"refs": [{"id": "ref-for-document"}], "title": "2.2.1. Supporting concepts"}], "external": true};
 window.dfnpanelData['129bdae8'] = {"dfnID": "129bdae8", "url": "https://dom.spec.whatwg.org/#event", "dfnText": "Event", "refSections": [{"refs": [{"id": "ref-for-event"}, {"id": "ref-for-event\u2460"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['d30f4c38'] = {"dfnID": "d30f4c38", "url": "https://dom.spec.whatwg.org/#callbackdef-eventlistener", "dfnText": "EventListener", "refSections": [{"refs": [{"id": "ref-for-callbackdef-eventlistener"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['2bc0cdf4'] = {"dfnID": "2bc0cdf4", "url": "https://dom.spec.whatwg.org/#eventtarget", "dfnText": "EventTarget", "refSections": [{"refs": [{"id": "ref-for-eventtarget"}, {"id": "ref-for-eventtarget\u2460"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['711357e0'] = {"dfnID": "711357e0", "url": "https://dom.spec.whatwg.org/#eventdef-abortsignal-abort", "dfnText": "abort", "refSections": [{"refs": [{"id": "ref-for-eventdef-abortsignal-abort"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
-window.dfnpanelData['28e64574'] = {"dfnID": "28e64574", "url": "https://dom.spec.whatwg.org/#abortsignal-abort-reason", "dfnText": "abort reason", "refSections": [{"refs": [{"id": "ref-for-abortsignal-abort-reason"}, {"id": "ref-for-abortsignal-abort-reason\u2460"}, {"id": "ref-for-abortsignal-abort-reason\u2461"}, {"id": "ref-for-abortsignal-abort-reason\u2462"}, {"id": "ref-for-abortsignal-abort-reason\u2463"}, {"id": "ref-for-abortsignal-abort-reason\u2464"}, {"id": "ref-for-abortsignal-abort-reason\u2465"}, {"id": "ref-for-abortsignal-abort-reason\u2466"}, {"id": "ref-for-abortsignal-abort-reason\u2467"}, {"id": "ref-for-abortsignal-abort-reason\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
-window.dfnpanelData['535dd335'] = {"dfnID": "535dd335", "url": "https://dom.spec.whatwg.org/#abortsignal-aborted", "dfnText": "aborted", "refSections": [{"refs": [{"id": "ref-for-abortsignal-aborted"}, {"id": "ref-for-abortsignal-aborted\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortsignal-aborted\u2461"}, {"id": "ref-for-abortsignal-aborted\u2462"}, {"id": "ref-for-abortsignal-aborted\u2463"}, {"id": "ref-for-abortsignal-aborted\u2464"}, {"id": "ref-for-abortsignal-aborted\u2465"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-abortsignal-aborted\u2466"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['87bc23a5'] = {"dfnID": "87bc23a5", "url": "https://dom.spec.whatwg.org/#abortsignal-add", "dfnText": "add", "refSections": [{"refs": [{"id": "ref-for-abortsignal-add"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortsignal-add\u2460"}, {"id": "ref-for-abortsignal-add\u2461"}, {"id": "ref-for-abortsignal-add\u2462"}, {"id": "ref-for-abortsignal-add\u2463"}, {"id": "ref-for-abortsignal-add\u2464"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['28e64574'] = {"dfnID": "28e64574", "url": "https://dom.spec.whatwg.org/#abortsignal-abort-reason", "dfnText": "abort reason", "refSections": [{"refs": [{"id": "ref-for-abortsignal-abort-reason"}, {"id": "ref-for-abortsignal-abort-reason\u2460"}, {"id": "ref-for-abortsignal-abort-reason\u2461"}, {"id": "ref-for-abortsignal-abort-reason\u2462"}, {"id": "ref-for-abortsignal-abort-reason\u2463"}, {"id": "ref-for-abortsignal-abort-reason\u2464"}, {"id": "ref-for-abortsignal-abort-reason\u2465"}, {"id": "ref-for-abortsignal-abort-reason\u2466"}, {"id": "ref-for-abortsignal-abort-reason\u2467"}, {"id": "ref-for-abortsignal-abort-reason\u2468"}, {"id": "ref-for-abortsignal-abort-reason\u2460\u24ea"}, {"id": "ref-for-abortsignal-abort-reason\u2460\u2460"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['535dd335'] = {"dfnID": "535dd335", "url": "https://dom.spec.whatwg.org/#abortsignal-aborted", "dfnText": "aborted", "refSections": [{"refs": [{"id": "ref-for-abortsignal-aborted"}, {"id": "ref-for-abortsignal-aborted\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortsignal-aborted\u2461"}, {"id": "ref-for-abortsignal-aborted\u2462"}, {"id": "ref-for-abortsignal-aborted\u2463"}, {"id": "ref-for-abortsignal-aborted\u2464"}, {"id": "ref-for-abortsignal-aborted\u2465"}, {"id": "ref-for-abortsignal-aborted\u2466"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-abortsignal-aborted\u2467"}], "title": "3. EventTarget integration"}], "external": true};
+window.dfnpanelData['87bc23a5'] = {"dfnID": "87bc23a5", "url": "https://dom.spec.whatwg.org/#abortsignal-add", "dfnText": "add", "refSections": [{"refs": [{"id": "ref-for-abortsignal-add"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortsignal-add\u2460"}, {"id": "ref-for-abortsignal-add\u2461"}, {"id": "ref-for-abortsignal-add\u2462"}, {"id": "ref-for-abortsignal-add\u2463"}, {"id": "ref-for-abortsignal-add\u2464"}, {"id": "ref-for-abortsignal-add\u2465"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['f99bafb9'] = {"dfnID": "f99bafb9", "url": "https://dom.spec.whatwg.org/#add-an-event-listener", "dfnText": "add an event listener", "refSections": [{"refs": [{"id": "ref-for-add-an-event-listener"}, {"id": "ref-for-add-an-event-listener\u2460"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['622d9f0e'] = {"dfnID": "622d9f0e", "url": "https://dom.spec.whatwg.org/#event-listener-callback", "dfnText": "callback", "refSections": [{"refs": [{"id": "ref-for-event-listener-callback"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['2e75f88e'] = {"dfnID": "2e75f88e", "url": "https://dom.spec.whatwg.org#event-listener-capture", "dfnText": "capture", "refSections": [{"refs": [{"id": "ref-for-event-listener-capture"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['c9db6cec'] = {"dfnID": "c9db6cec", "url": "https://dom.spec.whatwg.org/#create-a-dependent-abort-signal", "dfnText": "create a dependent abort signal", "refSections": [{"refs": [{"id": "ref-for-create-a-dependent-abort-signal"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-create-a-dependent-abort-signal\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-create-a-dependent-abort-signal\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-create-a-dependent-abort-signal\u2462"}, {"id": "ref-for-create-a-dependent-abort-signal\u2463"}, {"id": "ref-for-create-a-dependent-abort-signal\u2464"}, {"id": "ref-for-create-a-dependent-abort-signal\u2465"}, {"id": "ref-for-create-a-dependent-abort-signal\u2466"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['c9db6cec'] = {"dfnID": "c9db6cec", "url": "https://dom.spec.whatwg.org/#create-a-dependent-abort-signal", "dfnText": "create a dependent abort signal", "refSections": [{"refs": [{"id": "ref-for-create-a-dependent-abort-signal"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-create-a-dependent-abort-signal\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-create-a-dependent-abort-signal\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-create-a-dependent-abort-signal\u2462"}, {"id": "ref-for-create-a-dependent-abort-signal\u2463"}, {"id": "ref-for-create-a-dependent-abort-signal\u2464"}, {"id": "ref-for-create-a-dependent-abort-signal\u2465"}, {"id": "ref-for-create-a-dependent-abort-signal\u2466"}, {"id": "ref-for-create-a-dependent-abort-signal\u2467"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['15793b54'] = {"dfnID": "15793b54", "url": "https://dom.spec.whatwg.org#abortsignal-dependent-signals", "dfnText": "dependent signals", "refSections": [{"refs": [{"id": "ref-for-abortsignal-dependent-signals"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['06950d36'] = {"dfnID": "06950d36", "url": "https://dom.spec.whatwg.org/#concept-event-listener", "dfnText": "event listener", "refSections": [{"refs": [{"id": "ref-for-concept-event-listener"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['8fc9882c'] = {"dfnID": "8fc9882c", "url": "https://dom.spec.whatwg.org#event-listener-once", "dfnText": "once", "refSections": [{"refs": [{"id": "ref-for-event-listener-once"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['75264195'] = {"dfnID": "75264195", "url": "https://dom.spec.whatwg.org#event-listener-passive", "dfnText": "passive", "refSections": [{"refs": [{"id": "ref-for-event-listener-passive"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['0fe84b59'] = {"dfnID": "0fe84b59", "url": "https://dom.spec.whatwg.org/#abortcontroller-signal", "dfnText": "signal (for AbortController)", "refSections": [{"refs": [{"id": "ref-for-abortcontroller-signal"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortcontroller-signal\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortcontroller-signal\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortcontroller-signal\u2462"}, {"id": "ref-for-abortcontroller-signal\u2463"}, {"id": "ref-for-abortcontroller-signal\u2464"}, {"id": "ref-for-abortcontroller-signal\u2465"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['0fe84b59'] = {"dfnID": "0fe84b59", "url": "https://dom.spec.whatwg.org/#abortcontroller-signal", "dfnText": "signal (for AbortController)", "refSections": [{"refs": [{"id": "ref-for-abortcontroller-signal"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortcontroller-signal\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-abortcontroller-signal\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortcontroller-signal\u2462"}, {"id": "ref-for-abortcontroller-signal\u2463"}, {"id": "ref-for-abortcontroller-signal\u2464"}, {"id": "ref-for-abortcontroller-signal\u2465"}, {"id": "ref-for-abortcontroller-signal\u2466"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['3f076bc8'] = {"dfnID": "3f076bc8", "url": "https://dom.spec.whatwg.org#event-listener-signal", "dfnText": "signal (for event listener)", "refSections": [{"refs": [{"id": "ref-for-event-listener-signal"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['2296404c'] = {"dfnID": "2296404c", "url": "https://dom.spec.whatwg.org/#abortcontroller-signal-abort", "dfnText": "signal abort (for AbortController)", "refSections": [{"refs": [{"id": "ref-for-abortcontroller-signal-abort"}, {"id": "ref-for-abortcontroller-signal-abort\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortcontroller-signal-abort\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortcontroller-signal-abort\u2462"}, {"id": "ref-for-abortcontroller-signal-abort\u2463"}, {"id": "ref-for-abortcontroller-signal-abort\u2464"}, {"id": "ref-for-abortcontroller-signal-abort\u2465"}, {"id": "ref-for-abortcontroller-signal-abort\u2466"}, {"id": "ref-for-abortcontroller-signal-abort\u2467"}, {"id": "ref-for-abortcontroller-signal-abort\u2468"}, {"id": "ref-for-abortcontroller-signal-abort\u2460\u24ea"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['2296404c'] = {"dfnID": "2296404c", "url": "https://dom.spec.whatwg.org/#abortcontroller-signal-abort", "dfnText": "signal abort (for AbortController)", "refSections": [{"refs": [{"id": "ref-for-abortcontroller-signal-abort"}, {"id": "ref-for-abortcontroller-signal-abort\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-abortcontroller-signal-abort\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-abortcontroller-signal-abort\u2462"}, {"id": "ref-for-abortcontroller-signal-abort\u2463"}, {"id": "ref-for-abortcontroller-signal-abort\u2464"}, {"id": "ref-for-abortcontroller-signal-abort\u2465"}, {"id": "ref-for-abortcontroller-signal-abort\u2466"}, {"id": "ref-for-abortcontroller-signal-abort\u2467"}, {"id": "ref-for-abortcontroller-signal-abort\u2468"}, {"id": "ref-for-abortcontroller-signal-abort\u2460\u24ea"}, {"id": "ref-for-abortcontroller-signal-abort\u2460\u2460"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['0363f041'] = {"dfnID": "0363f041", "url": "https://dom.spec.whatwg.org#signal-abort", "dfnText": "signal abort (for AbortSignal)", "refSections": [{"refs": [{"id": "ref-for-signal-abort"}], "title": "2.3.2. Observable-returning operators"}], "external": true};
 window.dfnpanelData['3c3a94af'] = {"dfnID": "3c3a94af", "url": "https://dom.spec.whatwg.org#event-listener-type", "dfnText": "type", "refSections": [{"refs": [{"id": "ref-for-event-listener-type"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['3aec4bbc'] = {"dfnID": "3aec4bbc", "url": "https://tc39.es/ecma262/#current-realm", "dfnText": "current realm", "refSections": [{"refs": [{"id": "ref-for-current-realm"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-current-realm\u2460"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-current-realm\u2461"}, {"id": "ref-for-current-realm\u2462"}, {"id": "ref-for-current-realm\u2463"}, {"id": "ref-for-current-realm\u2464"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['3aec4bbc'] = {"dfnID": "3aec4bbc", "url": "https://tc39.es/ecma262/#current-realm", "dfnText": "current realm", "refSections": [{"refs": [{"id": "ref-for-current-realm"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-current-realm\u2460"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-current-realm\u2461"}, {"id": "ref-for-current-realm\u2462"}, {"id": "ref-for-current-realm\u2463"}, {"id": "ref-for-current-realm\u2464"}, {"id": "ref-for-current-realm\u2465"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['5d7209e9'] = {"dfnID": "5d7209e9", "url": "https://html.spec.whatwg.org/multipage/nav-history-apis.html#window", "dfnText": "Window", "refSections": [{"refs": [{"id": "ref-for-window"}, {"id": "ref-for-window\u2460"}, {"id": "ref-for-window\u2461"}, {"id": "ref-for-window\u2462"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-window\u2463"}, {"id": "ref-for-window\u2464"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-window\u2465"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['3349d69f'] = {"dfnID": "3349d69f", "url": "https://html.spec.whatwg.org/multipage/nav-history-apis.html#concept-document-window", "dfnText": "associated document", "refSections": [{"refs": [{"id": "ref-for-concept-document-window"}, {"id": "ref-for-concept-document-window\u2460"}, {"id": "ref-for-concept-document-window\u2461"}, {"id": "ref-for-concept-document-window\u2462"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-concept-document-window\u2463"}, {"id": "ref-for-concept-document-window\u2464"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-concept-document-window\u2465"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['0e3ba9f8'] = {"dfnID": "0e3ba9f8", "url": "https://html.spec.whatwg.org/multipage/document-sequences.html#fully-active", "dfnText": "fully active", "refSections": [{"refs": [{"id": "ref-for-fully-active"}, {"id": "ref-for-fully-active\u2460"}, {"id": "ref-for-fully-active\u2461"}, {"id": "ref-for-fully-active\u2462"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-fully-active\u2463"}, {"id": "ref-for-fully-active\u2464"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-fully-active\u2465"}], "title": "3. EventTarget integration"}], "external": true};
@@ -2885,20 +2955,20 @@ <h2 class="no-num no-ref heading settled" id="issues-index"><span class="content
 window.dfnpanelData['99c988d6'] = {"dfnID": "99c988d6", "url": "https://infra.spec.whatwg.org/#list-remove", "dfnText": "remove", "refSections": [{"refs": [{"id": "ref-for-list-remove"}], "title": "2.3.2. Observable-returning operators"}], "external": true};
 window.dfnpanelData['984221ca'] = {"dfnID": "984221ca", "url": "https://infra.spec.whatwg.org/#struct", "dfnText": "struct", "refSections": [{"refs": [{"id": "ref-for-struct"}, {"id": "ref-for-struct\u2460"}], "title": "2.2.1. Supporting concepts"}], "external": true};
 window.dfnpanelData['8855a9aa'] = {"dfnID": "8855a9aa", "url": "https://webidl.spec.whatwg.org/#idl-DOMString", "dfnText": "DOMString", "refSections": [{"refs": [{"id": "ref-for-idl-DOMString"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['bdbd19d1'] = {"dfnID": "bdbd19d1", "url": "https://webidl.spec.whatwg.org/#idl-promise", "dfnText": "Promise", "refSections": [{"refs": [{"id": "ref-for-idl-promise"}, {"id": "ref-for-idl-promise\u2460"}, {"id": "ref-for-idl-promise\u2461"}, {"id": "ref-for-idl-promise\u2462"}, {"id": "ref-for-idl-promise\u2463"}, {"id": "ref-for-idl-promise\u2464"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-promise\u2465"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['bdbd19d1'] = {"dfnID": "bdbd19d1", "url": "https://webidl.spec.whatwg.org/#idl-promise", "dfnText": "Promise", "refSections": [{"refs": [{"id": "ref-for-idl-promise"}, {"id": "ref-for-idl-promise\u2460"}, {"id": "ref-for-idl-promise\u2461"}, {"id": "ref-for-idl-promise\u2462"}, {"id": "ref-for-idl-promise\u2463"}, {"id": "ref-for-idl-promise\u2464"}, {"id": "ref-for-idl-promise\u2465"}, {"id": "ref-for-idl-promise\u2466"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-promise\u2467"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['7004c2a7'] = {"dfnID": "7004c2a7", "url": "https://webidl.spec.whatwg.org/#VoidFunction", "dfnText": "VoidFunction", "refSections": [{"refs": [{"id": "ref-for-VoidFunction"}, {"id": "ref-for-VoidFunction\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-VoidFunction\u2461"}, {"id": "ref-for-VoidFunction\u2462"}], "title": "2.2. The Observable interface"}], "external": true};
-window.dfnpanelData['dacde8b5'] = {"dfnID": "dacde8b5", "url": "https://webidl.spec.whatwg.org/#a-new-promise", "dfnText": "a new promise", "refSections": [{"refs": [{"id": "ref-for-a-new-promise"}, {"id": "ref-for-a-new-promise\u2460"}, {"id": "ref-for-a-new-promise\u2461"}, {"id": "ref-for-a-new-promise\u2462"}, {"id": "ref-for-a-new-promise\u2463"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['dacde8b5'] = {"dfnID": "dacde8b5", "url": "https://webidl.spec.whatwg.org/#a-new-promise", "dfnText": "a new promise", "refSections": [{"refs": [{"id": "ref-for-a-new-promise"}, {"id": "ref-for-a-new-promise\u2460"}, {"id": "ref-for-a-new-promise\u2461"}, {"id": "ref-for-a-new-promise\u2462"}, {"id": "ref-for-a-new-promise\u2463"}, {"id": "ref-for-a-new-promise\u2464"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['cc61f510'] = {"dfnID": "cc61f510", "url": "https://webidl.spec.whatwg.org/#an-exception-was-thrown", "dfnText": "an exception was thrown", "refSections": [{"refs": [{"id": "ref-for-an-exception-was-thrown"}, {"id": "ref-for-an-exception-was-thrown\u2460"}, {"id": "ref-for-an-exception-was-thrown\u2461"}, {"id": "ref-for-an-exception-was-thrown\u2462"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-an-exception-was-thrown\u2463"}, {"id": "ref-for-an-exception-was-thrown\u2464"}, {"id": "ref-for-an-exception-was-thrown\u2465"}, {"id": "ref-for-an-exception-was-thrown\u2466"}, {"id": "ref-for-an-exception-was-thrown\u2467"}, {"id": "ref-for-an-exception-was-thrown\u2468"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-an-exception-was-thrown\u2460\u24ea"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2460"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2461"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2462"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2463"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2464"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-an-exception-was-thrown\u2460\u2465"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2466"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2467"}, {"id": "ref-for-an-exception-was-thrown\u2460\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
-window.dfnpanelData['6c6b1005'] = {"dfnID": "6c6b1005", "url": "https://webidl.spec.whatwg.org/#idl-any", "dfnText": "any", "refSections": [{"refs": [{"id": "ref-for-idl-any"}, {"id": "ref-for-idl-any\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-idl-any\u2461"}, {"id": "ref-for-idl-any\u2462"}, {"id": "ref-for-idl-any\u2463"}, {"id": "ref-for-idl-any\u2464"}, {"id": "ref-for-idl-any\u2465"}, {"id": "ref-for-idl-any\u2466"}, {"id": "ref-for-idl-any\u2467"}, {"id": "ref-for-idl-any\u2468"}, {"id": "ref-for-idl-any\u2460\u24ea"}, {"id": "ref-for-idl-any\u2460\u2460"}, {"id": "ref-for-idl-any\u2460\u2461"}, {"id": "ref-for-idl-any\u2460\u2462"}, {"id": "ref-for-idl-any\u2460\u2463"}, {"id": "ref-for-idl-any\u2460\u2464"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-any\u2460\u2465"}, {"id": "ref-for-idl-any\u2460\u2466"}, {"id": "ref-for-idl-any\u2460\u2467"}, {"id": "ref-for-idl-any\u2460\u2468"}, {"id": "ref-for-idl-any\u2461\u24ea"}, {"id": "ref-for-idl-any\u2461\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-idl-any\u2461\u2461"}, {"id": "ref-for-idl-any\u2461\u2462"}, {"id": "ref-for-idl-any\u2461\u2463"}, {"id": "ref-for-idl-any\u2461\u2464"}, {"id": "ref-for-idl-any\u2461\u2465"}], "title": "2.3.2. Observable-returning operators"}], "external": true};
+window.dfnpanelData['6c6b1005'] = {"dfnID": "6c6b1005", "url": "https://webidl.spec.whatwg.org/#idl-any", "dfnText": "any", "refSections": [{"refs": [{"id": "ref-for-idl-any"}, {"id": "ref-for-idl-any\u2460"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-idl-any\u2461"}, {"id": "ref-for-idl-any\u2462"}, {"id": "ref-for-idl-any\u2463"}, {"id": "ref-for-idl-any\u2464"}, {"id": "ref-for-idl-any\u2465"}, {"id": "ref-for-idl-any\u2466"}, {"id": "ref-for-idl-any\u2467"}, {"id": "ref-for-idl-any\u2468"}, {"id": "ref-for-idl-any\u2460\u24ea"}, {"id": "ref-for-idl-any\u2460\u2460"}, {"id": "ref-for-idl-any\u2460\u2461"}, {"id": "ref-for-idl-any\u2460\u2462"}, {"id": "ref-for-idl-any\u2460\u2463"}, {"id": "ref-for-idl-any\u2460\u2464"}, {"id": "ref-for-idl-any\u2460\u2465"}, {"id": "ref-for-idl-any\u2460\u2466"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-any\u2460\u2467"}, {"id": "ref-for-idl-any\u2460\u2468"}, {"id": "ref-for-idl-any\u2461\u24ea"}, {"id": "ref-for-idl-any\u2461\u2460"}, {"id": "ref-for-idl-any\u2461\u2461"}, {"id": "ref-for-idl-any\u2461\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-idl-any\u2461\u2463"}, {"id": "ref-for-idl-any\u2461\u2464"}, {"id": "ref-for-idl-any\u2461\u2465"}, {"id": "ref-for-idl-any\u2461\u2466"}, {"id": "ref-for-idl-any\u2461\u2467"}], "title": "2.3.2. Observable-returning operators"}], "external": true};
 window.dfnpanelData['5372cca8'] = {"dfnID": "5372cca8", "url": "https://webidl.spec.whatwg.org/#idl-boolean", "dfnText": "boolean", "refSections": [{"refs": [{"id": "ref-for-idl-boolean"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-idl-boolean\u2460"}, {"id": "ref-for-idl-boolean\u2461"}, {"id": "ref-for-idl-boolean\u2462"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-boolean\u2463"}, {"id": "ref-for-idl-boolean\u2464"}], "title": "3. EventTarget integration"}], "external": true};
 window.dfnpanelData['3ab7bf79'] = {"dfnID": "3ab7bf79", "url": "https://webidl.spec.whatwg.org/#dfn-callback-function", "dfnText": "callback function", "refSections": [{"refs": [{"id": "ref-for-dfn-callback-function"}, {"id": "ref-for-dfn-callback-function\u2460"}, {"id": "ref-for-dfn-callback-function\u2461"}, {"id": "ref-for-dfn-callback-function\u2462"}], "title": "2.2.1. Supporting concepts"}], "external": true};
 window.dfnpanelData['10ce5f6f'] = {"dfnID": "10ce5f6f", "url": "https://webidl.spec.whatwg.org/#invoke-a-callback-function", "dfnText": "invoke", "refSections": [{"refs": [{"id": "ref-for-invoke-a-callback-function"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-invoke-a-callback-function\u2460"}, {"id": "ref-for-invoke-a-callback-function\u2461"}, {"id": "ref-for-invoke-a-callback-function\u2462"}, {"id": "ref-for-invoke-a-callback-function\u2463"}, {"id": "ref-for-invoke-a-callback-function\u2464"}, {"id": "ref-for-invoke-a-callback-function\u2465"}, {"id": "ref-for-invoke-a-callback-function\u2466"}, {"id": "ref-for-invoke-a-callback-function\u2467"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-invoke-a-callback-function\u2468"}, {"id": "ref-for-invoke-a-callback-function\u2460\u24ea"}, {"id": "ref-for-invoke-a-callback-function\u2460\u2460"}, {"id": "ref-for-invoke-a-callback-function\u2460\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-invoke-a-callback-function\u2460\u2462"}, {"id": "ref-for-invoke-a-callback-function\u2460\u2463"}, {"id": "ref-for-invoke-a-callback-function\u2460\u2464"}, {"id": "ref-for-invoke-a-callback-function\u2460\u2465"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
-window.dfnpanelData['56f81a8e'] = {"dfnID": "56f81a8e", "url": "https://webidl.spec.whatwg.org/#new", "dfnText": "new", "refSections": [{"refs": [{"id": "ref-for-new"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-new\u2460"}, {"id": "ref-for-new\u2461"}, {"id": "ref-for-new\u2462"}, {"id": "ref-for-new\u2463"}, {"id": "ref-for-new\u2464"}, {"id": "ref-for-new\u2465"}, {"id": "ref-for-new\u2466"}, {"id": "ref-for-new\u2467"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-new\u2468"}, {"id": "ref-for-new\u2460\u24ea"}, {"id": "ref-for-new\u2460\u2460"}, {"id": "ref-for-new\u2460\u2461"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-new\u2460\u2462"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['b262501e'] = {"dfnID": "b262501e", "url": "https://webidl.spec.whatwg.org/#reject", "dfnText": "reject", "refSections": [{"refs": [{"id": "ref-for-reject"}, {"id": "ref-for-reject\u2460"}, {"id": "ref-for-reject\u2461"}, {"id": "ref-for-reject\u2462"}, {"id": "ref-for-reject\u2463"}, {"id": "ref-for-reject\u2464"}, {"id": "ref-for-reject\u2465"}, {"id": "ref-for-reject\u2466"}, {"id": "ref-for-reject\u2467"}, {"id": "ref-for-reject\u2468"}, {"id": "ref-for-reject\u2460\u24ea"}, {"id": "ref-for-reject\u2460\u2460"}, {"id": "ref-for-reject\u2460\u2461"}, {"id": "ref-for-reject\u2460\u2462"}, {"id": "ref-for-reject\u2460\u2463"}, {"id": "ref-for-reject\u2460\u2464"}, {"id": "ref-for-reject\u2460\u2465"}, {"id": "ref-for-reject\u2460\u2466"}, {"id": "ref-for-reject\u2460\u2467"}, {"id": "ref-for-reject\u2460\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
-window.dfnpanelData['3b90bdcd'] = {"dfnID": "3b90bdcd", "url": "https://webidl.spec.whatwg.org/#resolve", "dfnText": "resolve", "refSections": [{"refs": [{"id": "ref-for-resolve"}, {"id": "ref-for-resolve\u2460"}, {"id": "ref-for-resolve\u2461"}, {"id": "ref-for-resolve\u2462"}, {"id": "ref-for-resolve\u2463"}, {"id": "ref-for-resolve\u2464"}, {"id": "ref-for-resolve\u2465"}, {"id": "ref-for-resolve\u2466"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['56f81a8e'] = {"dfnID": "56f81a8e", "url": "https://webidl.spec.whatwg.org/#new", "dfnText": "new", "refSections": [{"refs": [{"id": "ref-for-new"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-new\u2460"}, {"id": "ref-for-new\u2461"}, {"id": "ref-for-new\u2462"}, {"id": "ref-for-new\u2463"}, {"id": "ref-for-new\u2464"}, {"id": "ref-for-new\u2465"}, {"id": "ref-for-new\u2466"}, {"id": "ref-for-new\u2467"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-new\u2468"}, {"id": "ref-for-new\u2460\u24ea"}, {"id": "ref-for-new\u2460\u2460"}, {"id": "ref-for-new\u2460\u2461"}, {"id": "ref-for-new\u2460\u2462"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-new\u2460\u2463"}], "title": "3. EventTarget integration"}], "external": true};
+window.dfnpanelData['b262501e'] = {"dfnID": "b262501e", "url": "https://webidl.spec.whatwg.org/#reject", "dfnText": "reject", "refSections": [{"refs": [{"id": "ref-for-reject"}, {"id": "ref-for-reject\u2460"}, {"id": "ref-for-reject\u2461"}, {"id": "ref-for-reject\u2462"}, {"id": "ref-for-reject\u2463"}, {"id": "ref-for-reject\u2464"}, {"id": "ref-for-reject\u2465"}, {"id": "ref-for-reject\u2466"}, {"id": "ref-for-reject\u2467"}, {"id": "ref-for-reject\u2468"}, {"id": "ref-for-reject\u2460\u24ea"}, {"id": "ref-for-reject\u2460\u2460"}, {"id": "ref-for-reject\u2460\u2461"}, {"id": "ref-for-reject\u2460\u2462"}, {"id": "ref-for-reject\u2460\u2463"}, {"id": "ref-for-reject\u2460\u2464"}, {"id": "ref-for-reject\u2460\u2465"}, {"id": "ref-for-reject\u2460\u2466"}, {"id": "ref-for-reject\u2460\u2467"}, {"id": "ref-for-reject\u2460\u2468"}, {"id": "ref-for-reject\u2461\u24ea"}, {"id": "ref-for-reject\u2461\u2460"}, {"id": "ref-for-reject\u2461\u2461"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['3b90bdcd'] = {"dfnID": "3b90bdcd", "url": "https://webidl.spec.whatwg.org/#resolve", "dfnText": "resolve", "refSections": [{"refs": [{"id": "ref-for-resolve"}, {"id": "ref-for-resolve\u2460"}, {"id": "ref-for-resolve\u2461"}, {"id": "ref-for-resolve\u2462"}, {"id": "ref-for-resolve\u2463"}, {"id": "ref-for-resolve\u2464"}, {"id": "ref-for-resolve\u2465"}, {"id": "ref-for-resolve\u2466"}, {"id": "ref-for-resolve\u2467"}, {"id": "ref-for-resolve\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['9cce47fd'] = {"dfnID": "9cce47fd", "url": "https://webidl.spec.whatwg.org/#idl-sequence", "dfnText": "sequence", "refSections": [{"refs": [{"id": "ref-for-idl-sequence"}], "title": "2.2. The Observable interface"}], "external": true};
-window.dfnpanelData['4013a022'] = {"dfnID": "4013a022", "url": "https://webidl.spec.whatwg.org/#this", "dfnText": "this", "refSections": [{"refs": [{"id": "ref-for-this"}, {"id": "ref-for-this\u2460"}, {"id": "ref-for-this\u2461"}, {"id": "ref-for-this\u2462"}, {"id": "ref-for-this\u2463"}, {"id": "ref-for-this\u2464"}, {"id": "ref-for-this\u2465"}, {"id": "ref-for-this\u2466"}, {"id": "ref-for-this\u2467"}, {"id": "ref-for-this\u2468"}, {"id": "ref-for-this\u2460\u24ea"}, {"id": "ref-for-this\u2460\u2460"}, {"id": "ref-for-this\u2460\u2461"}, {"id": "ref-for-this\u2460\u2462"}, {"id": "ref-for-this\u2460\u2463"}, {"id": "ref-for-this\u2460\u2464"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-this\u2460\u2465"}, {"id": "ref-for-this\u2460\u2466"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-this\u2460\u2467"}, {"id": "ref-for-this\u2460\u2468"}, {"id": "ref-for-this\u2461\u24ea"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-this\u2461\u2460"}, {"id": "ref-for-this\u2461\u2461"}, {"id": "ref-for-this\u2461\u2462"}, {"id": "ref-for-this\u2461\u2463"}, {"id": "ref-for-this\u2461\u2464"}, {"id": "ref-for-this\u2461\u2465"}, {"id": "ref-for-this\u2461\u2466"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-this\u2461\u2467"}, {"id": "ref-for-this\u2461\u2468"}, {"id": "ref-for-this\u2462\u24ea"}, {"id": "ref-for-this\u2462\u2460"}, {"id": "ref-for-this\u2462\u2461"}, {"id": "ref-for-this\u2462\u2462"}, {"id": "ref-for-this\u2462\u2463"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-this\u2462\u2464"}, {"id": "ref-for-this\u2462\u2465"}], "title": "3. EventTarget integration"}], "external": true};
-window.dfnpanelData['5f90bbfb'] = {"dfnID": "5f90bbfb", "url": "https://webidl.spec.whatwg.org/#idl-undefined", "dfnText": "undefined", "refSections": [{"refs": [{"id": "ref-for-idl-undefined"}, {"id": "ref-for-idl-undefined\u2460"}, {"id": "ref-for-idl-undefined\u2461"}, {"id": "ref-for-idl-undefined\u2462"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-idl-undefined\u2463"}, {"id": "ref-for-idl-undefined\u2464"}, {"id": "ref-for-idl-undefined\u2465"}, {"id": "ref-for-idl-undefined\u2466"}, {"id": "ref-for-idl-undefined\u2467"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-undefined\u2468"}, {"id": "ref-for-idl-undefined\u2460\u24ea"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
+window.dfnpanelData['4013a022'] = {"dfnID": "4013a022", "url": "https://webidl.spec.whatwg.org/#this", "dfnText": "this", "refSections": [{"refs": [{"id": "ref-for-this"}, {"id": "ref-for-this\u2460"}, {"id": "ref-for-this\u2461"}, {"id": "ref-for-this\u2462"}, {"id": "ref-for-this\u2463"}, {"id": "ref-for-this\u2464"}, {"id": "ref-for-this\u2465"}, {"id": "ref-for-this\u2466"}, {"id": "ref-for-this\u2467"}, {"id": "ref-for-this\u2468"}, {"id": "ref-for-this\u2460\u24ea"}, {"id": "ref-for-this\u2460\u2460"}, {"id": "ref-for-this\u2460\u2461"}, {"id": "ref-for-this\u2460\u2462"}, {"id": "ref-for-this\u2460\u2463"}, {"id": "ref-for-this\u2460\u2464"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-this\u2460\u2465"}, {"id": "ref-for-this\u2460\u2466"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-this\u2460\u2467"}, {"id": "ref-for-this\u2460\u2468"}, {"id": "ref-for-this\u2461\u24ea"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-this\u2461\u2460"}, {"id": "ref-for-this\u2461\u2461"}, {"id": "ref-for-this\u2461\u2462"}, {"id": "ref-for-this\u2461\u2463"}, {"id": "ref-for-this\u2461\u2464"}, {"id": "ref-for-this\u2461\u2465"}, {"id": "ref-for-this\u2461\u2466"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-this\u2461\u2467"}, {"id": "ref-for-this\u2461\u2468"}, {"id": "ref-for-this\u2462\u24ea"}, {"id": "ref-for-this\u2462\u2460"}, {"id": "ref-for-this\u2462\u2461"}, {"id": "ref-for-this\u2462\u2462"}, {"id": "ref-for-this\u2462\u2463"}, {"id": "ref-for-this\u2462\u2464"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-this\u2462\u2465"}, {"id": "ref-for-this\u2462\u2466"}], "title": "3. EventTarget integration"}], "external": true};
+window.dfnpanelData['5f90bbfb'] = {"dfnID": "5f90bbfb", "url": "https://webidl.spec.whatwg.org/#idl-undefined", "dfnText": "undefined", "refSections": [{"refs": [{"id": "ref-for-idl-undefined"}, {"id": "ref-for-idl-undefined\u2460"}, {"id": "ref-for-idl-undefined\u2461"}, {"id": "ref-for-idl-undefined\u2462"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-idl-undefined\u2463"}, {"id": "ref-for-idl-undefined\u2464"}, {"id": "ref-for-idl-undefined\u2465"}, {"id": "ref-for-idl-undefined\u2466"}, {"id": "ref-for-idl-undefined\u2467"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-undefined\u2468"}, {"id": "ref-for-idl-undefined\u2460\u24ea"}, {"id": "ref-for-idl-undefined\u2460\u2460"}, {"id": "ref-for-idl-undefined\u2460\u2461"}, {"id": "ref-for-idl-undefined\u2460\u2462"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['f14b47b8'] = {"dfnID": "f14b47b8", "url": "https://webidl.spec.whatwg.org/#idl-unsigned-long-long", "dfnText": "unsigned long long", "refSections": [{"refs": [{"id": "ref-for-idl-unsigned-long-long"}, {"id": "ref-for-idl-unsigned-long-long\u2460"}, {"id": "ref-for-idl-unsigned-long-long\u2461"}, {"id": "ref-for-idl-unsigned-long-long\u2462"}, {"id": "ref-for-idl-unsigned-long-long\u2463"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-idl-unsigned-long-long\u2464"}, {"id": "ref-for-idl-unsigned-long-long\u2465"}, {"id": "ref-for-idl-unsigned-long-long\u2466"}, {"id": "ref-for-idl-unsigned-long-long\u2467"}, {"id": "ref-for-idl-unsigned-long-long\u2468"}, {"id": "ref-for-idl-unsigned-long-long\u2460\u24ea"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-idl-unsigned-long-long\u2460\u2460"}, {"id": "ref-for-idl-unsigned-long-long\u2460\u2461"}, {"id": "ref-for-idl-unsigned-long-long\u2460\u2462"}, {"id": "ref-for-idl-unsigned-long-long\u2460\u2463"}], "title": "2.3.3. Promise-returning operators"}], "external": true};
 window.dfnpanelData['subscriber'] = {"dfnID": "subscriber", "url": "#subscriber", "dfnText": "Subscriber", "refSections": [{"refs": [{"id": "ref-for-subscriber"}, {"id": "ref-for-subscriber\u2460"}, {"id": "ref-for-subscriber\u2461"}, {"id": "ref-for-subscriber\u2462"}, {"id": "ref-for-subscriber\u2463"}, {"id": "ref-for-subscriber\u2464"}, {"id": "ref-for-subscriber\u2465"}, {"id": "ref-for-subscriber\u2466"}, {"id": "ref-for-subscriber\u2467"}, {"id": "ref-for-subscriber\u2468"}, {"id": "ref-for-subscriber\u2460\u24ea"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-subscriber\u2460\u2460"}, {"id": "ref-for-subscriber\u2460\u2461"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-subscriber\u2460\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-subscriber\u2460\u2463"}, {"id": "ref-for-subscriber\u2460\u2464"}, {"id": "ref-for-subscriber\u2460\u2465"}, {"id": "ref-for-subscriber\u2460\u2466"}, {"id": "ref-for-subscriber\u2460\u2467"}, {"id": "ref-for-subscriber\u2460\u2468"}, {"id": "ref-for-subscriber\u2461\u24ea"}, {"id": "ref-for-subscriber\u2461\u2460"}, {"id": "ref-for-subscriber\u2461\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-subscriber\u2461\u2462"}, {"id": "ref-for-subscriber\u2461\u2463"}], "title": "3. EventTarget integration"}], "external": false};
 window.dfnpanelData['subscriber-next-algorithm'] = {"dfnID": "subscriber-next-algorithm", "url": "#subscriber-next-algorithm", "dfnText": "next algorithm", "refSections": [{"refs": [{"id": "ref-for-subscriber-next-algorithm"}, {"id": "ref-for-subscriber-next-algorithm\u2460"}, {"id": "ref-for-subscriber-next-algorithm\u2461"}, {"id": "ref-for-subscriber-next-algorithm\u2462"}, {"id": "ref-for-subscriber-next-algorithm\u2463"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-subscriber-next-algorithm\u2464"}], "title": "2.2.1. Supporting concepts"}], "external": false};
@@ -2922,23 +2992,23 @@ <h2 class="no-num no-ref heading settled" id="issues-index"><span class="content
 window.dfnpanelData['dom-subscriptionobserver-error'] = {"dfnID": "dom-subscriptionobserver-error", "url": "#dom-subscriptionobserver-error", "dfnText": "error", "refSections": [{"refs": [{"id": "ref-for-dom-subscriptionobserver-error"}, {"id": "ref-for-dom-subscriptionobserver-error\u2460"}, {"id": "ref-for-dom-subscriptionobserver-error\u2461"}, {"id": "ref-for-dom-subscriptionobserver-error\u2462"}, {"id": "ref-for-dom-subscriptionobserver-error\u2463"}], "title": "2.2.1. Supporting concepts"}], "external": false};
 window.dfnpanelData['dom-subscriptionobserver-complete'] = {"dfnID": "dom-subscriptionobserver-complete", "url": "#dom-subscriptionobserver-complete", "dfnText": "complete", "refSections": [{"refs": [{"id": "ref-for-dom-subscriptionobserver-complete"}, {"id": "ref-for-dom-subscriptionobserver-complete\u2460"}, {"id": "ref-for-dom-subscriptionobserver-complete\u2461"}, {"id": "ref-for-dom-subscriptionobserver-complete\u2462"}], "title": "2.2.1. Supporting concepts"}], "external": false};
 window.dfnpanelData['typedefdef-observerunion'] = {"dfnID": "typedefdef-observerunion", "url": "#typedefdef-observerunion", "dfnText": "ObserverUnion", "refSections": [{"refs": [{"id": "ref-for-typedefdef-observerunion"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-typedefdef-observerunion\u2460"}, {"id": "ref-for-typedefdef-observerunion\u2461"}], "title": "2.2.1. Supporting concepts"}], "external": false};
-window.dfnpanelData['dictdef-subscribeoptions'] = {"dfnID": "dictdef-subscribeoptions", "url": "#dictdef-subscribeoptions", "dfnText": "SubscribeOptions", "refSections": [{"refs": [{"id": "ref-for-dictdef-subscribeoptions"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2460"}, {"id": "ref-for-dictdef-subscribeoptions\u2461"}, {"id": "ref-for-dictdef-subscribeoptions\u2462"}, {"id": "ref-for-dictdef-subscribeoptions\u2463"}, {"id": "ref-for-dictdef-subscribeoptions\u2464"}, {"id": "ref-for-dictdef-subscribeoptions\u2465"}, {"id": "ref-for-dictdef-subscribeoptions\u2466"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2467"}, {"id": "ref-for-dictdef-subscribeoptions\u2468"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2460\u24ea"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2460"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2461"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2462"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2463"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2464"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2465"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2466"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2467"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2460\u2468"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u24ea"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2460"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2461"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2462"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2461\u2463"}], "title": "3. EventTarget integration"}], "external": false};
-window.dfnpanelData['dom-subscribeoptions-signal'] = {"dfnID": "dom-subscribeoptions-signal", "url": "#dom-subscribeoptions-signal", "dfnText": "signal", "refSections": [{"refs": [{"id": "ref-for-dom-subscribeoptions-signal"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-dom-subscribeoptions-signal\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-dom-subscribeoptions-signal\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2460"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-dom-subscribeoptions-signal\u2460\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2465"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
+window.dfnpanelData['dictdef-subscribeoptions'] = {"dfnID": "dictdef-subscribeoptions", "url": "#dictdef-subscribeoptions", "dfnText": "SubscribeOptions", "refSections": [{"refs": [{"id": "ref-for-dictdef-subscribeoptions"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2460"}, {"id": "ref-for-dictdef-subscribeoptions\u2461"}, {"id": "ref-for-dictdef-subscribeoptions\u2462"}, {"id": "ref-for-dictdef-subscribeoptions\u2463"}, {"id": "ref-for-dictdef-subscribeoptions\u2464"}, {"id": "ref-for-dictdef-subscribeoptions\u2465"}, {"id": "ref-for-dictdef-subscribeoptions\u2466"}, {"id": "ref-for-dictdef-subscribeoptions\u2467"}, {"id": "ref-for-dictdef-subscribeoptions\u2468"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2460\u24ea"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2460"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2460\u2461"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2462"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2463"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2464"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2465"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2466"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2467"}, {"id": "ref-for-dictdef-subscribeoptions\u2460\u2468"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u24ea"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2461\u2460"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2461"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2462"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2463"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2464"}, {"id": "ref-for-dictdef-subscribeoptions\u2461\u2465"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-dictdef-subscribeoptions\u2461\u2466"}], "title": "3. EventTarget integration"}], "external": false};
+window.dfnpanelData['dom-subscribeoptions-signal'] = {"dfnID": "dom-subscribeoptions-signal", "url": "#dom-subscribeoptions-signal", "dfnText": "signal", "refSections": [{"refs": [{"id": "ref-for-dom-subscribeoptions-signal"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-dom-subscribeoptions-signal\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-dom-subscribeoptions-signal\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2460"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-dom-subscribeoptions-signal\u2460\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2460\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2461\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2462\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2461"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2462"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2463"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2464"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2465"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2466"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2467"}, {"id": "ref-for-dom-subscribeoptions-signal\u2463\u2468"}, {"id": "ref-for-dom-subscribeoptions-signal\u2464\u24ea"}, {"id": "ref-for-dom-subscribeoptions-signal\u2464\u2460"}, {"id": "ref-for-dom-subscribeoptions-signal\u2464\u2461"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
 window.dfnpanelData['callbackdef-predicate'] = {"dfnID": "callbackdef-predicate", "url": "#callbackdef-predicate", "dfnText": "Predicate", "refSections": [{"refs": [{"id": "ref-for-callbackdef-predicate"}, {"id": "ref-for-callbackdef-predicate\u2460"}, {"id": "ref-for-callbackdef-predicate\u2461"}, {"id": "ref-for-callbackdef-predicate\u2462"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['callbackdef-reducer'] = {"dfnID": "callbackdef-reducer", "url": "#callbackdef-reducer", "dfnText": "Reducer", "refSections": [{"refs": [{"id": "ref-for-callbackdef-reducer"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['callbackdef-mapper'] = {"dfnID": "callbackdef-mapper", "url": "#callbackdef-mapper", "dfnText": "Mapper", "refSections": [{"refs": [{"id": "ref-for-callbackdef-mapper"}, {"id": "ref-for-callbackdef-mapper\u2460"}, {"id": "ref-for-callbackdef-mapper\u2461"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-callbackdef-mapper\u2462"}, {"id": "ref-for-callbackdef-mapper\u2463"}], "title": "2.3.2. Observable-returning operators"}], "external": false};
 window.dfnpanelData['callbackdef-visitor'] = {"dfnID": "callbackdef-visitor", "url": "#callbackdef-visitor", "dfnText": "Visitor", "refSections": [{"refs": [{"id": "ref-for-callbackdef-visitor"}], "title": "2.2. The Observable interface"}], "external": false};
-window.dfnpanelData['observable'] = {"dfnID": "observable", "url": "#observable", "dfnText": "Observable", "refSections": [{"refs": [{"id": "ref-for-observable"}, {"id": "ref-for-observable\u2460"}, {"id": "ref-for-observable\u2461"}, {"id": "ref-for-observable\u2462"}, {"id": "ref-for-observable\u2463"}, {"id": "ref-for-observable\u2464"}, {"id": "ref-for-observable\u2465"}, {"id": "ref-for-observable\u2466"}, {"id": "ref-for-observable\u2467"}, {"id": "ref-for-observable\u2468"}, {"id": "ref-for-observable\u2460\u24ea"}, {"id": "ref-for-observable\u2460\u2460"}, {"id": "ref-for-observable\u2460\u2461"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-observable\u2460\u2462"}, {"id": "ref-for-observable\u2460\u2463"}, {"id": "ref-for-observable\u2460\u2464"}, {"id": "ref-for-observable\u2460\u2465"}, {"id": "ref-for-observable\u2460\u2466"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-observable\u2460\u2467"}, {"id": "ref-for-observable\u2460\u2468"}, {"id": "ref-for-observable\u2461\u24ea"}, {"id": "ref-for-observable\u2461\u2460"}, {"id": "ref-for-observable\u2461\u2461"}, {"id": "ref-for-observable\u2461\u2462"}, {"id": "ref-for-observable\u2461\u2463"}, {"id": "ref-for-observable\u2461\u2464"}, {"id": "ref-for-observable\u2461\u2465"}, {"id": "ref-for-observable\u2461\u2466"}, {"id": "ref-for-observable\u2461\u2467"}, {"id": "ref-for-observable\u2461\u2468"}, {"id": "ref-for-observable\u2462\u24ea"}, {"id": "ref-for-observable\u2462\u2460"}, {"id": "ref-for-observable\u2462\u2461"}, {"id": "ref-for-observable\u2462\u2462"}, {"id": "ref-for-observable\u2462\u2463"}, {"id": "ref-for-observable\u2462\u2464"}, {"id": "ref-for-observable\u2462\u2465"}, {"id": "ref-for-observable\u2462\u2466"}, {"id": "ref-for-observable\u2462\u2467"}, {"id": "ref-for-observable\u2462\u2468"}, {"id": "ref-for-observable\u2463\u24ea"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-observable\u2463\u2460"}, {"id": "ref-for-observable\u2463\u2461"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-observable\u2463\u2462"}, {"id": "ref-for-observable\u2463\u2463"}, {"id": "ref-for-observable\u2463\u2464"}], "title": "3. EventTarget integration"}, {"refs": [{"id": "ref-for-observable\u2463\u2465"}], "title": "5. Acknowledgements"}], "external": false};
+window.dfnpanelData['observable'] = {"dfnID": "observable", "url": "#observable", "dfnText": "Observable", "refSections": [{"refs": [{"id": "ref-for-observable"}, {"id": "ref-for-observable\u2460"}, {"id": "ref-for-observable\u2461"}, {"id": "ref-for-observable\u2462"}, {"id": "ref-for-observable\u2463"}, {"id": "ref-for-observable\u2464"}, {"id": "ref-for-observable\u2465"}, {"id": "ref-for-observable\u2466"}, {"id": "ref-for-observable\u2467"}, {"id": "ref-for-observable\u2468"}, {"id": "ref-for-observable\u2460\u24ea"}, {"id": "ref-for-observable\u2460\u2460"}, {"id": "ref-for-observable\u2460\u2461"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-observable\u2460\u2462"}, {"id": "ref-for-observable\u2460\u2463"}, {"id": "ref-for-observable\u2460\u2464"}, {"id": "ref-for-observable\u2460\u2465"}, {"id": "ref-for-observable\u2460\u2466"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-observable\u2460\u2467"}, {"id": "ref-for-observable\u2460\u2468"}, {"id": "ref-for-observable\u2461\u24ea"}, {"id": "ref-for-observable\u2461\u2460"}, {"id": "ref-for-observable\u2461\u2461"}, {"id": "ref-for-observable\u2461\u2462"}, {"id": "ref-for-observable\u2461\u2463"}, {"id": "ref-for-observable\u2461\u2464"}, {"id": "ref-for-observable\u2461\u2465"}, {"id": "ref-for-observable\u2461\u2466"}, {"id": "ref-for-observable\u2461\u2467"}, {"id": "ref-for-observable\u2461\u2468"}, {"id": "ref-for-observable\u2462\u24ea"}, {"id": "ref-for-observable\u2462\u2460"}, {"id": "ref-for-observable\u2462\u2461"}, {"id": "ref-for-observable\u2462\u2462"}, {"id": "ref-for-observable\u2462\u2463"}, {"id": "ref-for-observable\u2462\u2464"}, {"id": "ref-for-observable\u2462\u2465"}, {"id": "ref-for-observable\u2462\u2466"}, {"id": "ref-for-observable\u2462\u2467"}, {"id": "ref-for-observable\u2462\u2468"}, {"id": "ref-for-observable\u2463\u24ea"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-observable\u2463\u2460"}, {"id": "ref-for-observable\u2463\u2461"}, {"id": "ref-for-observable\u2463\u2462"}], "title": "2.3.3. Promise-returning operators"}, {"refs": [{"id": "ref-for-observable\u2463\u2463"}, {"id": "ref-for-observable\u2463\u2464"}, {"id": "ref-for-observable\u2463\u2465"}], "title": "3. EventTarget integration"}, {"refs": [{"id": "ref-for-observable\u2463\u2466"}], "title": "5. Acknowledgements"}], "external": false};
 window.dfnpanelData['dom-observable-from'] = {"dfnID": "dom-observable-from", "url": "#dom-observable-from", "dfnText": "from", "refSections": [{"refs": [{"id": "ref-for-dom-observable-from"}, {"id": "ref-for-dom-observable-from\u2460"}], "title": "2.3.1. from()"}, {"refs": [{"id": "ref-for-dom-observable-from\u2461"}, {"id": "ref-for-dom-observable-from\u2462"}, {"id": "ref-for-dom-observable-from\u2463"}], "title": "2.3.2. Observable-returning operators"}], "external": false};
 window.dfnpanelData['observable-subscribe-callback'] = {"dfnID": "observable-subscribe-callback", "url": "#observable-subscribe-callback", "dfnText": "subscribe callback", "refSections": [{"refs": [{"id": "ref-for-observable-subscribe-callback"}, {"id": "ref-for-observable-subscribe-callback\u2460"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-observable-subscribe-callback\u2461"}, {"id": "ref-for-observable-subscribe-callback\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-observable-subscribe-callback\u2463"}, {"id": "ref-for-observable-subscribe-callback\u2464"}, {"id": "ref-for-observable-subscribe-callback\u2465"}, {"id": "ref-for-observable-subscribe-callback\u2466"}, {"id": "ref-for-observable-subscribe-callback\u2467"}, {"id": "ref-for-observable-subscribe-callback\u2468"}, {"id": "ref-for-observable-subscribe-callback\u2460\u24ea"}, {"id": "ref-for-observable-subscribe-callback\u2460\u2460"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-observable-subscribe-callback\u2460\u2461"}], "title": "3. EventTarget integration"}], "external": false};
 window.dfnpanelData['dom-observable-observable'] = {"dfnID": "dom-observable-observable", "url": "#dom-observable-observable", "dfnText": "new\n  Observable(callback)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-observable"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-subscribe'] = {"dfnID": "dom-observable-subscribe", "url": "#dom-observable-subscribe", "dfnText": "subscribe(observer, options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-subscribe"}, {"id": "ref-for-dom-observable-subscribe\u2460"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-dom-observable-subscribe\u2461"}, {"id": "ref-for-dom-observable-subscribe\u2462"}, {"id": "ref-for-dom-observable-subscribe\u2463"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-dom-observable-subscribe\u2464"}], "title": "3. EventTarget integration"}], "external": false};
 window.dfnpanelData['default-error-algorithm'] = {"dfnID": "default-error-algorithm", "url": "#default-error-algorithm", "dfnText": "default error algorithm", "refSections": [{"refs": [{"id": "ref-for-default-error-algorithm"}, {"id": "ref-for-default-error-algorithm\u2460"}], "title": "2.2.1. Supporting concepts"}], "external": false};
-window.dfnpanelData['internal-observer'] = {"dfnID": "internal-observer", "url": "#internal-observer", "dfnText": "internal observer", "refSections": [{"refs": [{"id": "ref-for-internal-observer"}, {"id": "ref-for-internal-observer\u2460"}, {"id": "ref-for-internal-observer\u2461"}, {"id": "ref-for-internal-observer\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer\u2463"}, {"id": "ref-for-internal-observer\u2464"}, {"id": "ref-for-internal-observer\u2465"}, {"id": "ref-for-internal-observer\u2466"}, {"id": "ref-for-internal-observer\u2467"}, {"id": "ref-for-internal-observer\u2468"}, {"id": "ref-for-internal-observer\u2460\u24ea"}, {"id": "ref-for-internal-observer\u2460\u2460"}, {"id": "ref-for-internal-observer\u2460\u2461"}, {"id": "ref-for-internal-observer\u2460\u2462"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer\u2460\u2463"}, {"id": "ref-for-internal-observer\u2460\u2464"}, {"id": "ref-for-internal-observer\u2460\u2465"}, {"id": "ref-for-internal-observer\u2460\u2466"}, {"id": "ref-for-internal-observer\u2460\u2467"}, {"id": "ref-for-internal-observer\u2460\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
-window.dfnpanelData['internal-observer-next-steps'] = {"dfnID": "internal-observer-next-steps", "url": "#internal-observer-next-steps", "dfnText": "next steps", "refSections": [{"refs": [{"id": "ref-for-internal-observer-next-steps"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-internal-observer-next-steps\u2460"}, {"id": "ref-for-internal-observer-next-steps\u2461"}, {"id": "ref-for-internal-observer-next-steps\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer-next-steps\u2463"}, {"id": "ref-for-internal-observer-next-steps\u2464"}, {"id": "ref-for-internal-observer-next-steps\u2465"}, {"id": "ref-for-internal-observer-next-steps\u2466"}, {"id": "ref-for-internal-observer-next-steps\u2467"}, {"id": "ref-for-internal-observer-next-steps\u2468"}, {"id": "ref-for-internal-observer-next-steps\u2460\u24ea"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2460"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2461"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2462"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer-next-steps\u2460\u2463"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2464"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2465"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2466"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2467"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2468"}, {"id": "ref-for-internal-observer-next-steps\u2461\u24ea"}, {"id": "ref-for-internal-observer-next-steps\u2461\u2460"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
-window.dfnpanelData['internal-observer-error-steps'] = {"dfnID": "internal-observer-error-steps", "url": "#internal-observer-error-steps", "dfnText": "error steps", "refSections": [{"refs": [{"id": "ref-for-internal-observer-error-steps"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-internal-observer-error-steps\u2460"}, {"id": "ref-for-internal-observer-error-steps\u2461"}, {"id": "ref-for-internal-observer-error-steps\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer-error-steps\u2463"}, {"id": "ref-for-internal-observer-error-steps\u2464"}, {"id": "ref-for-internal-observer-error-steps\u2465"}, {"id": "ref-for-internal-observer-error-steps\u2466"}, {"id": "ref-for-internal-observer-error-steps\u2467"}, {"id": "ref-for-internal-observer-error-steps\u2468"}, {"id": "ref-for-internal-observer-error-steps\u2460\u24ea"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2460"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2461"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2462"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer-error-steps\u2460\u2463"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2464"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2465"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2466"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2467"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
-window.dfnpanelData['internal-observer-complete-steps'] = {"dfnID": "internal-observer-complete-steps", "url": "#internal-observer-complete-steps", "dfnText": "complete steps", "refSections": [{"refs": [{"id": "ref-for-internal-observer-complete-steps"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-internal-observer-complete-steps\u2460"}, {"id": "ref-for-internal-observer-complete-steps\u2461"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer-complete-steps\u2462"}, {"id": "ref-for-internal-observer-complete-steps\u2463"}, {"id": "ref-for-internal-observer-complete-steps\u2464"}, {"id": "ref-for-internal-observer-complete-steps\u2465"}, {"id": "ref-for-internal-observer-complete-steps\u2466"}, {"id": "ref-for-internal-observer-complete-steps\u2467"}, {"id": "ref-for-internal-observer-complete-steps\u2468"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u24ea"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2460"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer-complete-steps\u2460\u2462"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2463"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2464"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2465"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2466"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2467"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
-window.dfnpanelData['observable-subscribe-to-an-observable'] = {"dfnID": "observable-subscribe-to-an-observable", "url": "#observable-subscribe-to-an-observable", "dfnText": "subscribe to an Observable", "refSections": [{"refs": [{"id": "ref-for-observable-subscribe-to-an-observable"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-observable-subscribe-to-an-observable\u2460"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-observable-subscribe-to-an-observable\u2463"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2464"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2465"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2466"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2467"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2468"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u24ea"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2460"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2461"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2462"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2463"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2464"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2465"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2466"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2467"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2468"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461\u24ea"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461\u2460"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
+window.dfnpanelData['internal-observer'] = {"dfnID": "internal-observer", "url": "#internal-observer", "dfnText": "internal observer", "refSections": [{"refs": [{"id": "ref-for-internal-observer"}, {"id": "ref-for-internal-observer\u2460"}, {"id": "ref-for-internal-observer\u2461"}, {"id": "ref-for-internal-observer\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer\u2463"}, {"id": "ref-for-internal-observer\u2464"}, {"id": "ref-for-internal-observer\u2465"}, {"id": "ref-for-internal-observer\u2466"}, {"id": "ref-for-internal-observer\u2467"}, {"id": "ref-for-internal-observer\u2468"}, {"id": "ref-for-internal-observer\u2460\u24ea"}, {"id": "ref-for-internal-observer\u2460\u2460"}, {"id": "ref-for-internal-observer\u2460\u2461"}, {"id": "ref-for-internal-observer\u2460\u2462"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer\u2460\u2463"}, {"id": "ref-for-internal-observer\u2460\u2464"}, {"id": "ref-for-internal-observer\u2460\u2465"}, {"id": "ref-for-internal-observer\u2460\u2466"}, {"id": "ref-for-internal-observer\u2460\u2467"}, {"id": "ref-for-internal-observer\u2460\u2468"}, {"id": "ref-for-internal-observer\u2461\u24ea"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
+window.dfnpanelData['internal-observer-next-steps'] = {"dfnID": "internal-observer-next-steps", "url": "#internal-observer-next-steps", "dfnText": "next steps", "refSections": [{"refs": [{"id": "ref-for-internal-observer-next-steps"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-internal-observer-next-steps\u2460"}, {"id": "ref-for-internal-observer-next-steps\u2461"}, {"id": "ref-for-internal-observer-next-steps\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer-next-steps\u2463"}, {"id": "ref-for-internal-observer-next-steps\u2464"}, {"id": "ref-for-internal-observer-next-steps\u2465"}, {"id": "ref-for-internal-observer-next-steps\u2466"}, {"id": "ref-for-internal-observer-next-steps\u2467"}, {"id": "ref-for-internal-observer-next-steps\u2468"}, {"id": "ref-for-internal-observer-next-steps\u2460\u24ea"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2460"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2461"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2462"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer-next-steps\u2460\u2463"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2464"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2465"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2466"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2467"}, {"id": "ref-for-internal-observer-next-steps\u2460\u2468"}, {"id": "ref-for-internal-observer-next-steps\u2461\u24ea"}, {"id": "ref-for-internal-observer-next-steps\u2461\u2460"}, {"id": "ref-for-internal-observer-next-steps\u2461\u2461"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
+window.dfnpanelData['internal-observer-error-steps'] = {"dfnID": "internal-observer-error-steps", "url": "#internal-observer-error-steps", "dfnText": "error steps", "refSections": [{"refs": [{"id": "ref-for-internal-observer-error-steps"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-internal-observer-error-steps\u2460"}, {"id": "ref-for-internal-observer-error-steps\u2461"}, {"id": "ref-for-internal-observer-error-steps\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer-error-steps\u2463"}, {"id": "ref-for-internal-observer-error-steps\u2464"}, {"id": "ref-for-internal-observer-error-steps\u2465"}, {"id": "ref-for-internal-observer-error-steps\u2466"}, {"id": "ref-for-internal-observer-error-steps\u2467"}, {"id": "ref-for-internal-observer-error-steps\u2468"}, {"id": "ref-for-internal-observer-error-steps\u2460\u24ea"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2460"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2461"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2462"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer-error-steps\u2460\u2463"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2464"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2465"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2466"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2467"}, {"id": "ref-for-internal-observer-error-steps\u2460\u2468"}, {"id": "ref-for-internal-observer-error-steps\u2461\u24ea"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
+window.dfnpanelData['internal-observer-complete-steps'] = {"dfnID": "internal-observer-complete-steps", "url": "#internal-observer-complete-steps", "dfnText": "complete steps", "refSections": [{"refs": [{"id": "ref-for-internal-observer-complete-steps"}], "title": "2.1. The Subscriber interface"}, {"refs": [{"id": "ref-for-internal-observer-complete-steps\u2460"}, {"id": "ref-for-internal-observer-complete-steps\u2461"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-internal-observer-complete-steps\u2462"}, {"id": "ref-for-internal-observer-complete-steps\u2463"}, {"id": "ref-for-internal-observer-complete-steps\u2464"}, {"id": "ref-for-internal-observer-complete-steps\u2465"}, {"id": "ref-for-internal-observer-complete-steps\u2466"}, {"id": "ref-for-internal-observer-complete-steps\u2467"}, {"id": "ref-for-internal-observer-complete-steps\u2468"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u24ea"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2460"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2461"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-internal-observer-complete-steps\u2460\u2462"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2463"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2464"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2465"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2466"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2467"}, {"id": "ref-for-internal-observer-complete-steps\u2460\u2468"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
+window.dfnpanelData['observable-subscribe-to-an-observable'] = {"dfnID": "observable-subscribe-to-an-observable", "url": "#observable-subscribe-to-an-observable", "dfnText": "subscribe to an Observable", "refSections": [{"refs": [{"id": "ref-for-observable-subscribe-to-an-observable"}], "title": "2.2. The Observable interface"}, {"refs": [{"id": "ref-for-observable-subscribe-to-an-observable\u2460"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2462"}], "title": "2.2.1. Supporting concepts"}, {"refs": [{"id": "ref-for-observable-subscribe-to-an-observable\u2463"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2464"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2465"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2466"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2467"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2468"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u24ea"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2460"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2461"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2462"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2463"}], "title": "2.3.2. Observable-returning operators"}, {"refs": [{"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2464"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2465"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2466"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2467"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2460\u2468"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461\u24ea"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461\u2460"}, {"id": "ref-for-observable-subscribe-to-an-observable\u2461\u2461"}], "title": "2.3.3. Promise-returning operators"}], "external": false};
 window.dfnpanelData['dom-observable-takeuntil'] = {"dfnID": "dom-observable-takeuntil", "url": "#dom-observable-takeuntil", "dfnText": "takeUntil(notifier)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-takeuntil"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-map'] = {"dfnID": "dom-observable-map", "url": "#dom-observable-map", "dfnText": "map(mapper)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-map"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-filter'] = {"dfnID": "dom-observable-filter", "url": "#dom-observable-filter", "dfnText": "filter(predicate)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-filter"}], "title": "2.2. The Observable interface"}], "external": false};
@@ -2952,6 +3022,8 @@ <h2 class="no-num no-ref heading settled" id="issues-index"><span class="content
 window.dfnpanelData['dom-observable-toarray'] = {"dfnID": "dom-observable-toarray", "url": "#dom-observable-toarray", "dfnText": "toArray(options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-toarray"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-foreach'] = {"dfnID": "dom-observable-foreach", "url": "#dom-observable-foreach", "dfnText": "forEach(callback, options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-foreach"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-every'] = {"dfnID": "dom-observable-every", "url": "#dom-observable-every", "dfnText": "every(predicate, options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-every"}], "title": "2.2. The Observable interface"}], "external": false};
+window.dfnpanelData['dom-observable-first'] = {"dfnID": "dom-observable-first", "url": "#dom-observable-first", "dfnText": "first(options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-first"}], "title": "2.2. The Observable interface"}], "external": false};
+window.dfnpanelData['dom-observable-last'] = {"dfnID": "dom-observable-last", "url": "#dom-observable-last", "dfnText": "last(options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-last"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-find'] = {"dfnID": "dom-observable-find", "url": "#dom-observable-find", "dfnText": "find(predicate, options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-find"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-some'] = {"dfnID": "dom-observable-some", "url": "#dom-observable-some", "dfnText": "some(predicate, options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-some"}], "title": "2.2. The Observable interface"}], "external": false};
 window.dfnpanelData['dom-observable-reduce'] = {"dfnID": "dom-observable-reduce", "url": "#dom-observable-reduce", "dfnText": "reduce(reducer, initialValue, options)", "refSections": [{"refs": [{"id": "ref-for-dom-observable-reduce"}], "title": "2.2. The Observable interface"}], "external": false};