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Set.prototype.size - JavaScript | MDN
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Set.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 Set instances returns the number of (unique) elements in this set.
Try it
const set = new Set();
const object = {};
set.add(42);
set.add("forty two");
set.add("forty two");
set.add(object);
console.log(set.size);
// Expected output: 3
Description
The value of size is an integer representing how many entries the Set object has. A set accessor function for size is undefined; 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); // 3
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-get-set.prototype.size |
Browser compatibility
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