README.md

jq-web

This is a WebAssembly build of jq, the command-line JSON processor.

It runs in the browser.

Installation and use

npm install jq-web

var jq = require('jq-web');

jq.then( jq => jq.json({
  a: {
    big: {
      json: [
        'full',
        'of',
        'important',
        'things'
      ]
    }
  }
}, '.a.big.json | ["empty", .[1], "useless", .[3]] | join(" ")')

The code above returns the string "empty of useless things".

You could do the same using the promised API with jq.promised.json({...}).then(result => {}). That is useful if you're loading a .mem or .wasm file, as the library won't return the correct results until these files are asynchronously fetched by the Emscripten runtime.

Webpack issues

fs

The Emscripten runtime will try to require the fs module, and if it fails it will resort to an in-memory filesystem (almost no use of that is made of the library, but it is needed somehow). In Browserify there's a default {} that corresponds to the fs module, but in Webpack you must declare it as an empty module.

404 error when loading .wasm files

By default projects compiled with Emscripten look for .wasm files in the same directory that the .js file is run from. This causes issues when using webpack because name of the .wasm file is altered with a hash and can be placed in a different directory. To fix this problem you can use the copy-webpack-plugin to copy the jq.wasm file to the same directory that the webpack bundle is placed.

Reference

jq-web exports a promise that resolves to an object with json and raw methods.

jq.json(<object>, <filter>) <object> will take a Javascript object, or scalar, whatever, and dump it to JSON, then it will return whatever your filter outputs and try to convert that into a JS object.

jq.raw(<json-string>, <filter>, <flags>) <raw-output> will take a string that will be passed as it is to jq (like if you were doing echo '<json-string>' | jq <filter> on the command line) then return a string with the raw STDOUT response.

Build

1. Install Emscripten. There have been several API changes over time; version 3.1.31 is known to work.
2. Clone this repository, and cd into it.
3. make
   • This may take a while if you have never run Emscripten before.

Test

A handful of tests exist in test.js. These are a good place to start when verifying a build. To run them, do make test.

You can test browser functionality by running: ./node_modules/live-server/live-server.js --open="index.html".