async.js

const sleep_st = (t) => new Promise((r) => setTimeout(r, t));
const sleep_im = () => new Promise((r) => setImmediate(r));

(async () => {
  setImmediate(() => console.log(1));
  console.log(2);
  await sleep_st(0);
  setImmediate(() => console.log(3));
  console.log(4);
  await sleep_im();
  setImmediate(() => console.log(5));
  console.log(6);
  await 1;
  setImmediate(() => console.log(7));
  console.log(8);
})();