const weakSet = new WeakSet();

const obj1 = { name: 'First' };
const obj2 = { name: 'Second' };
const obj3 = obj1;

weakSet.add(obj1);
weakSet.add(obj2);

let result = '';
result += weakSet.has(obj1) + ', ';
result += weakSet.has(obj3) + ', ';

obj2.name = 'Modified';
result += weakSet.has(obj2) + ', ';

weakSet.delete(obj1);
result += weakSet.has(obj3);

console.log(result);