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The size accessor property of Set instances returns the number of (unique) elements in this set.
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
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.
const mySet = new Set();
mySet.add(1);
mySet.add(5);
mySet.add("some text");
console.log(mySet.size); // 3
| Specification |
|---|
| ECMAScript 2027 LanguageSpecification # sec-get-set.prototype.size |
This page was last modified on Jul 20, 2025 by MDN contributors.
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