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The keys()
method returns a new Iterator
object that contains the keys for each element in the Map
object in insertion order.
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 | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Map.prototype.keys' in that specification. |
Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Map.prototype.keys' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 38 | 20 (20) | No support | 25 | 7.1 |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | 38 | 20.0 (20) | No support | No support | 8 |