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 Latest Draft (ECMA-262) The definition of 'Map.prototype.keys' in that specification. |
Draft |
Browser compatibility
| Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|---|
| Basic support | 38 | (Yes) | 20 (20) | No support | 25 | 7.1 |
| Feature | Android | Chrome for Android | Edge | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|---|
| Basic support | No support | 38 | (Yes) | 20.0 (20) | No support | No support | 8 |