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javascript instance method

Set.prototype.has()

View on MDN ↗

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

Interactive exampleOpen the canonical MDN source to run this embedded demo.
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

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also