const wm = new WeakMap();
let obj1 = { name: 'John' };
let obj2 = { name: 'Jane' };
wm.set(obj1, 'developer');
wm.set(obj2, 'designer');
console.log(wm.get(obj1));
console.log(wm.has(obj2));
obj1 = null;
console.log(wm.get(obj1));
const normalObj = {};
try {
wm.set('string', 'value');
} catch (e) {
console.log('error');
}
Ответ: developer true undefined error
JavaScript test | #JavaScript & Max