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()

js
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