The has() method of WeakSet instances returns a boolean indicating whether the specified value exists in this WeakSet or not.
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: falsehas(value)valueThe value to test for presence in the WeakSet object. Objects are compared by reference, not by 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.
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);