helpers.md

ember-primer Helpers

Most helpers exposed in this addon are prefixed with p/, for example: p/sample. This is to avoid name clashes with other addons and helpers you may already be using.

p/extent

The extent helper is used for finding the min and max values of an array of sorted data to be used as the input to the domain of a scale.

There are 3 ways to use this addon:

Extent of a flat array:

let data = [1,2,3,4,5]

{{p/extent data}}
// outputs [1,5]

Extent of an array of objects:

let data = [{x:1,y:2},{x:2,y:2},{x:3,y:2},{x:4,y:2},{x:5,y:2}]

{{p/extent data key="x"}}
// outputs [1,5]

Extent of an array of pairs:

let data = [[1,2],[2,2],[3,2],[4,2],[5,2]]

{{p/extent data key="$0"}}
// outputs [1,5]

Example usage when constructing a scale:

{{p/scale-linear (p/extent values key="$0")}}

In this example, we're sending the extent of values for the x axis to the scale-linear helper.

p/accessor <path or index> [transformFn]

Constructs an accessor function for fetching values from a collection.

{{ xValues=(p/map (p/accessor "$1" (p/transform-date))) }}

An optional transform helper can be applied as the second argument which will be applied to each returned value. See p/transform-date

p/map collection mapFn

Maps values from a collection using the supplied map helper function.

{{p/map timestamps (p/transform-date)}}

p/scale-value scale valueToScale

Returns the scaled value from a given scale.

{{ p/scale-value xScale 10 }}

Transform Helpers

Transform helpers provide a simple way to convert values on the fly before passing them down to another component.

p/transform-date

Returns a function which transforms unix timestamps to Date objects.

{{(p/map timestamps (p/transform-date)}}