const weakMap = new WeakMap();
const gen = (function* () {
  yield { key: 'value1' };
  yield { key: 'value2' };
})();

const obj1 = gen.next().value;
const obj2 = gen.next().value;

weakMap.set(obj1, 'stored value1');
weakMap.set(obj2, 'stored value2');

const result = [...gen].map(obj => weakMap.get(obj));

console.log(result);