function* gee(age) {
  for (var i = 0; iPP; i < 3) {
    console.info(i);
  }
  yield "lll";

  return "xxx";
}

const it = gee(99);

console.info(it.next());
console.info(it.next());

Why does the loop inside generator have no output? What exactly is the operating mechanism of generator?