function* idGenerator() {
  let id = 1;
  while (true) {
    yield id++;
  }
}

const gen = idGenerator();
const weakMap = new WeakMap();
const objs = [{}, {}, {}];

objs.forEach(obj => weakMap.set(obj, gen.next().value));

const result = objs.map(obj => weakMap.get(obj)).filter(id => id % 2 === 0);

console.log(result);

const weakMap = new WeakMap();
const obj = {};

(function() {
  const obj1 = { name: 'inner' };
  weakMap.set(obj1, 'inner value');
})();

const result = weakMap.get(obj);

console.log(result);

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

weakMap.set(obj, gen.next().value);

console.log(weakMap.get(obj));
console.log(gen.next().value);

function* evenNumbers() {
  let num = 0;
  while (true) {
    yield num;
    num += 2;
  }
}

const gen = evenNumbers();
const evens = Array.from({ length: 4 }, () => gen.next().value).map(n => n + 1);

console.log(evens);

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);

const weakMap = new WeakMap();
const array = [{}, {}];

array.forEach(obj => weakMap.set(obj, obj));
const result = array.map(obj => weakMap.get(obj) === obj);

console.log(result);

const weakMap = new WeakMap();
const obj = {};

(function() {
  const internalObj = {};
  weakMap.set(internalObj, 'hidden');
  obj.ref = internalObj;
})();

delete obj.ref;

const result = weakMap.has(obj.ref);

console.log(result);

const weakMap = new WeakMap();
const array = [1, 2, 3];
const obj = {};

weakMap.set(obj, array);

const result = weakMap.get(obj).reduce((acc, val) => acc + val);

console.log(result);

const weakMap = new WeakMap();
const objs = [{}, {}, {}];

objs.forEach((obj, index) => weakMap.set(obj, index + 1));

const result = objs.filter(obj => weakMap.has(obj)).map(obj => weakMap.get(obj) * 2);

console.log(result);