Map.prototype.keys() - JavaScript 编辑

The keys() method returns a new Iterator object that contains the keys for each element in the Map object in insertion order.

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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

myMap.keys()

Return value

A new Map iterator object.

Examples

Using keys()

var myMap = new Map();
myMap.set('0', 'foo');
myMap.set(1, 'bar');
myMap.set({}, 'baz');

var mapIter = myMap.keys();

console.log(mapIter.next().value); // "0"
console.log(mapIter.next().value); // 1
console.log(mapIter.next().value); // Object

Specifications

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

Browser compatibility

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See also

• Map.prototype.entries()
• Map.prototype.values()