WeakSet.prototype.has() - JavaScript | MDN
Try it
const weakset = new WeakSet();
const object1 = {};
const object2 = {};
weakset.add(object1);
console.log(weakset.has(object1));
// Expected output: true
console.log(weakset.has(object2));
// Expected output: false
Syntax
Parameters
Return value
Returns true if the specified value exists in the WeakSet object; otherwise false. Always returns false if value is not an object or a non-registered symbol.
Examples
Using has()
js
const ws = new WeakSet();
const obj = {};
ws.add(window);
ws.has(window); // returns true
ws.has(obj); // returns false
// Storing a non-registered symbol
const sym = Symbol("foo");
ws.add(sym);
ws.add(Symbol.iterator);
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-weakset.prototype.has |