map.groupby ^{[![Version Badge][npm-version-svg]][package-url]}

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An ESnext spec-compliant Map.groupBy shim/polyfill/replacement that works as far down as ES3.

This package implements the es-shim API interface. It works in an ES3-supported environment and complies with the proposed spec.

Note: Safari 16 implements Array.prototype.groupToMap, but it does not work properly with strings containing surrogate pairs.

Getting started

``sh
npm install --save map.groupby
`

Usage/Examples

`js
var groupBy = require('map.groupby');
var assert = require('assert');

var arr = [0, 1, 2, 3, 4, 5];
var parity = function (x) { return x % 2 === 0 ? 'even' : 'odd'; };

var results = groupBy(arr, function (x, i) {
assert.equal(x, arr[i]);
return parity(x);
});

assert.deepEqual(results, new Map([
['even', [0, 2, 4]],
['odd', [1, 3, 5]],
]));
`

`js
var groupBy = require('map.groupby');
var assert = require('assert');
/ when Map.groupBy is not present /
delete Map.groupBy;
var shimmed = groupBy.shim();

assert.equal(shimmed, groupBy.getPolyfill());
assert.deepEqual(Map.groupBy(arr, parity), groupBy(arr, parity));
`

`js
var groupBy = require('map.groupby');
var assert = require('assert');
/ when Array#group is present /
var shimmed = groupBy.shim();

assert.equal(shimmed, Map.groupBy);
assert.deepEqual(Map.groupBy(arr, parity), groupBy(arr, parity));
`

Tests


Simply clone the repo, npm install, and run npm test`

[package-url]: https://npmjs.org/package/map.groupby
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