iter-sub-or-for-await.js

// utils
async function* foo() {
  for (let i = 0; i < 3; i++) {
    await new Promise((r) => setTimeout(r, 1000));
    yield i;
  }
}

const subToIter = (cb) => {
  const it = foo();
  const next = () => {
    it.next().then((item) => {
      if (!item.done) {
        cb(item.value);
        next();
      }
    });
  };
  next();
};

(async () => {
  console.log("before");
  subToIter((x) => console.log("sub", x));
  console.log("after");

  console.log("before for await");
  for await (const x of foo()) {
    console.log("for", x);
  }
  console.log("after for await");
})();