Set.prototype.has() - JavaScript | MDN (original) (raw)

Baseline

Widely available

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

Try it

const set1 = new Set([1, 2, 3, 4, 5]);

console.log(set1.has(1));
// Expected output: true

console.log(set1.has(5));
// Expected output: true

console.log(set1.has(6));
// Expected output: false

Syntax

Parameters

value

The value to test for presence in the Set object.

Return value

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

Examples

Using the has() method

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

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

const set1 = new Set();
const obj1 = { key1: 1 };
set1.add(obj1);

console.log(set1.has(obj1)); // true
console.log(set1.has({ key1: 1 })); // false, because they are different object references
console.log(set1.add({ key1: 1 })); // now set1 contains 2 entries

Specifications

Browser compatibility

See also