Set.prototype.has()
Returns whether a value exists in a Set.
Syntax
set.has(value)
Returns
boolean — `true` if the value is a member of the set.
Examples
const s = new Set([1, 2, 3]);
console.log(s.has(2));
console.log(s.has(5));
Output
true
false
const obj = {};
const s = new Set([obj]);
console.log(s.has(obj));
console.log(s.has({}));
Output
true
false
Notes
- Membership uses SameValueZero, so distinct objects are never equal.
- O(1) average lookup, faster than `Array.prototype.includes()` for
large collections.
Browser & runtime support
| Environment | Since version |
|---|---|
| chrome | 38 |
| firefox | 13 |
| safari | 8 |
| edge | 12 |
| node | 0.12 |