# array.prototype.keys <sup>[![Version Badge][npm-version-svg]][package-url]</sup>

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An ES2015 spec-compliant `Array.prototype.keys` shim/polyfill/replacement that works as far down as ES3.

This package implements the [es-shim API](https://github.com/es-shims/api) interface. It works in an ES3-supported environment and complies with the [spec](https://www.ecma-international.org/ecma-262/6.0/).

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

## Example

```js
var keys = require('array.prototype.keys');
var assert = require('assert');
var iterate = require('iterate-iterator');

assert.deepEqual(iterate(keys([1, 2, 3])), [0, 1, 2]);
assert.deepEqual(iterate(keys([1, 0, 1])), [0, 1, 2]);
assert.deepEqual(iterate(keys([NaN])), [0]);
assert.deepEqual(iterate(keys([1,,3])), [0, 1, 2]);
```

```js
var keys = require('array.prototype.keys');
var assert = require('assert');
/* when Array#keys is not present */
delete Array.prototype.keys;
var shimmedMap = keys.shim();
assert.deepEqual(shimmedMap, keys.getPolyfill());
assert.deepEqual(iterate([1, 2, 3].keys()), [0, 1, 2]);
assert.deepEqual(iterate([1, 0, 1].keys()), [0, 1, 2]);
assert.deepEqual(iterate([NaN].keys()), [0]);
assert.deepEqual(iterate([1,,3].keys()), [0, 1, 2]);
```

```js
var keys = require('array.prototype.keys');
var assert = require('assert');
/* when Array#keys is present */
var shimmedMap = keys.shim();
assert.equal(shimmedMap, Array.prototype.keys);
assert.deepEqual(iterate([1, 2, 3].keys()), [0, 1, 2]);
```

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

[package-url]: https://npmjs.org/package/array.prototype.keys
[npm-version-svg]: https://versionbadg.es/es-shims/Array.prototype.keys.svg
[deps-svg]: https://david-dm.org/es-shims/Array.prototype.keys.svg
[deps-url]: https://david-dm.org/es-shims/Array.prototype.keys
[dev-deps-svg]: https://david-dm.org/es-shims/Array.prototype.keys/dev-status.svg
[dev-deps-url]: https://david-dm.org/es-shims/Array.prototype.keys#info=devDependencies
[npm-badge-png]: https://nodei.co/npm/array.prototype.keys.png?downloads=true&stars=true
[license-image]: https://img.shields.io/npm/l/array.prototype.keys.svg
[license-url]: LICENSE
[downloads-image]: https://img.shields.io/npm/dm/array.prototype.keys.svg
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[codecov-image]: https://codecov.io/gh/es-shims/Array.prototype.keys/branch/main/graphs/badge.svg
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[actions-url]: https://github.com/es-shims/Array.prototype.keys/actions