Web/JavaScript/Reference/Global objects/Map/size

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

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`size`	Chrome Full support 38	Edge Full support 12	Firefox Full support 19 Notes' Full support 19 Notes' Notes' From Firefox 13 to Firefox 18, 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.	IE Full support 11	Opera Full support 25	Safari Full support 8	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 19 Notes' Full support 19 Notes' Notes' From Firefox 13 to Firefox 18, 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.	Opera Android Full support 25	Safari iOS Full support 8	Samsung Internet Android Full support 3.0	nodejs Full support 0.12

Legend

Full support: Full support
See implementation notes.': See implementation notes.