map.groupby

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.

Getting started

npm install --save map.groupby

Usage/Examples

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]],
]));

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));

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