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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	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 compatibilityUpdate compatibility data on GitHub

	Desktop
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	38	12	19 19 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.	11	25	8

	Mobile
	Android webview	Chrome for Android	Edge Mobile	Firefox for Android	Opera for Android	iOS Safari	Samsung Internet
Basic support	38	38	12	19 19 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.	25	8	Yes

	Server
	Node.js
Basic support	0.12