Set.prototype.size
BaselineWidely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Thesize accessor property ofSet instances returns the number of (unique) elements in this set.
Try it
const set1 = new Set();const object1 = {};set1.add(42);set1.add("forty two");set1.add("forty two");set1.add(object1);console.log(set1.size);// Expected output: 3Description
The value ofsize is an integer representing how many entries theSet object has. A set accessor function forsize isundefined; you cannot change this property.
Examples
Using size
js
const mySet = new Set();mySet.add(1);mySet.add(5);mySet.add("some text");console.log(mySet.size); // 3Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-get-set.prototype.size |