The size accessor property returns the number of elements in a Map object.
Description
The value of size is an integer representing how many entries the Map object has. A set accessor function for size is undefined; you can not change this property.
Examples
Using size
var myMap = new Map();
myMap.set('a', 'alpha');
myMap.set('b', 'beta');
myMap.set('g', 'gamma');
myMap.size // 3
Specifications
| Specification | Status | Comment |
|---|---|---|
| ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Map.prototype.size' in that specification. |
Standard | Initial definition. |
| ECMAScript Latest Draft (ECMA-262) The definition of 'Map.prototype.size' in that specification. |
Draft |
Browser compatibility
| Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|---|
| Basic support | 38 | (Yes) | 19 (19) | 11 | 25 | 7.1 |
| Feature | Android | Chrome for Android | Edge | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|---|
| Basic support | No support | 38 | (Yes) | 19.0 (19) | No support | No support | 8 |
Gecko-specific notes
- From Gecko 13 (Firefox 13 / Thunderbird 13 / SeaMonkey 2.10) to Gecko 18 (Firefox 18 / Thunderbird 18 / SeaMonkey 2.15 / Firefox OS 1.0.1 / Firefox OS 1.1) the size property was implemented as a
Map.prototype.size()method, this has been changed to a property in later versions conform to the ECMAScript 2015 specification (bug 807001).