Map.prototype.size

Baseline Widely available

This feature is well established and works across many devices and browser versions. It's been available across browsers since July 2015.

The size accessor property of Map instances returns the number of elements in this map.

Try it

const map = new Map();

map.set("a", "alpha");
map.set("b", "beta");
map.set("g", "gamma");

console.log(map.size);
// Expected output: 3

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 cannot change this property.

Examples

Using size

const myMap = new Map();
myMap.set("a", "alpha");
myMap.set("b", "beta");
myMap.set("g", "gamma");

console.log(myMap.size); // 3

Specifications

Specification
ECMAScript® 2027 Language Specification # sec-get-map.prototype.size

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`size`	38	12	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	38	19 From Firefox for Android 14 to Firefox for Android 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	3.0	38	8	1.0.0	1.0	0.12.0