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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

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Array.prototype.keys' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Array.prototype.keys' in that specification.
Draft  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support38 Yes28 No258
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes28 Yes8 Yes

See also

Document Tags and Contributors

 Last updated by: wbamberg,