array.prototype.groupby

array.prototype.groupby

An ESnext spec-compliant Array.prototype.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.

Because Array.prototype.groupBy depends on a receiver (the this value), the main export takes the array to operate on as the first argument.

Getting started

npm install --save array.prototype.groupby

Usage/Examples

var groupBy = require('array.prototype.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, a) {
    assert.equal(x, arr[i]);
    assert.equal(a, arr);
    return parity(x);
});

assert.deepEqual(results, {
    __proto__: null,
    even: [0, 2, 4],
    odd: [1, 3, 5],
});

var groupBy = require('array.prototype.groupby');
var assert = require('assert');
/* when Array#groupBy is not present */
delete Array.prototype.groupBy;
var shimmed = groupBy.shim();

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

var groupBy = require('array.prototype.groupby');
var assert = require('assert');
/* when Array#groupBy is present */
var shimmed = groupBy.shim();

assert.equal(shimmed, Array.prototype.groupBy);
assert.deepEqual(arr.groupBy(parity), groupBy(arr, parity));

Tests

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