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Set.prototype.has()

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 has() method of Set instances returns a boolean indicating whether the specified value exists in this Set or not.

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

has(value)

Parameters

value: The value to test for presence in the Set object.

Return value

Returns true if the specified value exists in the Set object; otherwise false.

Examples

Using has()

const mySet = new Set();
mySet.add("foo");

console.log(mySet.has("foo")); // true
console.log(mySet.has("bar")); // false

const set = new Set();
const obj = { key1: 1 };
set.add(obj);

console.log(set.has(obj)); // true
console.log(set.has({ key1: 1 })); // false, because they are different object references
console.log(set.add({ key1: 1 })); // now set contains 2 entries

Specifications

Specification
ECMAScript® 2026 Language Specification> # sec-set.prototype.has>

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`has`	38	12	13	25	8	38	14	25	8	3.0	38	8	1.0.0	1.0	0.12.0