The keys() method returns a new iterator object that contains the keys for each element in the Map object in insertion order. In this particular case, this iterator object is also an iterable, so a for...of loop can be used.
Map.prototype.keys()
Try it
Syntax
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
Browser compatibility
| Desktop | Mobile | Server | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
keys |
38
|
12
|
20
|
No
|
25
|
8
|
38
|
38
|
20
|
25
|
8
|
3.0
|
1.0
|
0.12.0
|
See also
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/keys
