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.
Thehas() method ofSet instances returns a boolean indicating whether the specified value exists in thisSet or not.
Try it
const set = new Set([1, 2, 3, 4, 5]);console.log(set.has(1));// Expected output: trueconsole.log(set.has(5));// Expected output: trueconsole.log(set.has(6));// Expected output: falseSyntax
js
has(value)Parameters
valueThe value to test for presence in the
Setobject.
Return value
Returnstrue if the specified value exists in theSet object; otherwisefalse.
Examples
Using has()
js
const mySet = new Set();mySet.add("foo");console.log(mySet.has("foo")); // trueconsole.log(mySet.has("bar")); // falseconst set = new Set();const obj = { key1: 1 };set.add(obj);console.log(set.has(obj)); // trueconsole.log(set.has({ key1: 1 })); // false, because they are different object referencesconsole.log(set.add({ key1: 1 })); // now set contains 2 entriesSpecifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-set.prototype.has |