Set() constructor
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 Set() constructor creates Set objects.
Try it
const set = new Set([1, 2, 3, 4, 5]);
console.log(set.has(1));
// Expected output: true
console.log(set.has(5));
// Expected output: true
console.log(set.has(6));
// Expected output: false
Syntax
js
new Set()
new Set(iterable)
Parameters
iterableOptional-
If an iterable object (such as an array) is passed, all of its elements will be added to the new
Set. If you don't specify this parameter, or its value isnullorundefined, the newSetis empty.
Return value
A new Set object.
Examples
Using the Set object
js
const mySet = new Set();
mySet.add(1); // Set [ 1 ]
mySet.add(5); // Set [ 1, 5 ]
mySet.add(5); // Set [ 1, 5 ]
mySet.add("some text"); // Set [ 1, 5, 'some text' ]
const o = { a: 1, b: 2 };
mySet.add(o);
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-set-constructor |
Browser compatibility
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