Array.prototype.keys() - JavaScript 编辑

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

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The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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
ECMAScript (ECMA-262) The definition of 'Array.prototype.keys' in that specification.

Browser compatibility

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See also

• Array.prototype.values()
• Array.prototype.entries()
• Iteration protocols