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array.keys

The keys() method returns a new Array Iterator object that contains the keys for each index in the array.

Syntax

arr.keys()

Return value

A new Array iterator object.

Examples

Key iterator doesn't ignore holes

var arr = ['a', , 'c'];
var sparseKeys = Object.keys(arr);
var denseKeys = [...arr.keys()];
console.log(sparseKeys); // ['0', '2']
console.log(denseKeys);  // [0, 1, 2]

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
keys 38 12 28 No 25 8
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
keys 38 38 28 25 8 3.0
Server
Node.js
keys 0.12

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/keys