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
js
has(value)
Parameters
value-
The value to test for presence in the
Setobject.
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
Specifications
| Specification |
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| ECMAScript® 2027 Language Specification # sec-set.prototype.has |
Browser compatibility
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Legend
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