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 map1 = new Map();

map1.set("a", "alpha");
map1.set("b", "beta");
map1.set("g", "gamma");

console.log(map1.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 can not change this property.

Examples

Using size

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

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

Specifications

Specification
ECMAScript® 2025 Language Specification
# sec-get-map.prototype.size

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
size

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
See implementation notes.

See also