1# array.prototype.flatmap <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
2
3[![Build Status][travis-svg]][travis-url]
4[![dependency status][deps-svg]][deps-url]
5[![dev dependency status][dev-deps-svg]][dev-deps-url]
6[![License][license-image]][license-url]
7[![Downloads][downloads-image]][downloads-url]
8
9[![npm badge][npm-badge-png]][package-url]
10
11An ESnext spec-compliant `Array.prototype.flatMap` shim/polyfill/replacement that works as far down as ES3.
12
13This package implements the [es-shim API](https://github.com/es-shims/api) interface. It works in an ES3-supported environment and complies with the proposed [spec](https://tc39.github.io/proposal-flatMap/).
14
15Because `Array.prototype.flatMap` depends on a receiver (the `this` value), the main export takes the array to operate on as the first argument.
16
17## Getting started
18
19```sh
20npm install --save array.prototype.flatmap
21```
22
23## Usage/Examples
24
25```js
26var flatMap = require('array.prototype.flatmap');
27var assert = require('assert');
28
29var arr = [1, [2], [], 3];
30
31var results = flatMap(arr, function (x, i) {
32	assert.equal(x, arr[i]);
33	return x;
34});
35
36assert.deepEqual(results, [1, 2, 3]);
37```
38
39```js
40var flatMap = require('array.prototype.flatmap');
41var assert = require('assert');
42/* when Array#flatMap is not present */
43delete Array.prototype.flatMap;
44var shimmedFlatMap = flatMap.shim();
45
46var mapper = function (x) { return [x, 1]; };
47
48assert.equal(shimmedFlatMap, flatMap.getPolyfill());
49assert.deepEqual(arr.flatMap(mapper), flatMap(arr, mapper));
50```
51
52```js
53var flatMap = require('array.prototype.flatmap');
54var assert = require('assert');
55/* when Array#flatMap is present */
56var shimmedIncludes = flatMap.shim();
57
58var mapper = function (x) { return [x, 1]; };
59
60assert.equal(shimmedIncludes, Array.prototype.flatMap);
61assert.deepEqual(arr.flatMap(mapper), flatMap(arr, mapper));
62```
63
64## Tests
65Simply clone the repo, `npm install`, and run `npm test`
66
67[package-url]: https://npmjs.org/package/array.prototype.flatmap
68[npm-version-svg]: http://versionbadg.es/es-shims/Array.prototype.flatMap.svg
69[travis-svg]: https://travis-ci.org/es-shims/Array.prototype.flatMap.svg
70[travis-url]: https://travis-ci.org/es-shims/Array.prototype.flatMap
71[deps-svg]: https://david-dm.org/es-shims/Array.prototype.flatMap.svg
72[deps-url]: https://david-dm.org/es-shims/Array.prototype.flatMap
73[dev-deps-svg]: https://david-dm.org/es-shims/Array.prototype.flatMap/dev-status.svg
74[dev-deps-url]: https://david-dm.org/es-shims/Array.prototype.flatMap#info=devDependencies
75[npm-badge-png]: https://nodei.co/npm/array.prototype.flatmap.png?downloads=true&stars=true
76[license-image]: http://img.shields.io/npm/l/array.prototype.flatmap.svg
77[license-url]: LICENSE
78[downloads-image]: http://img.shields.io/npm/dm/array.prototype.flatmap.svg
79[downloads-url]: http://npm-stat.com/charts.html?package=array.prototype.flatmap
80