async_generators.js

const delay = ms => new Promise(res => setTimeount(res, ms));

async function * gen() {
  await delay(1000);
  yield 1;
  await delay(1000);
  yield 2;
  await delay(1000);
  yield 3;
}

// асинхронная итерация
async function main() {
  for await (const value of gen()) {
    console.log(value);
  }
}

// аналог
async function def() {
  const generator = gen();
  while (true) {
    const { value, done } = await generator.next();
    if (done) {
      break;
    }
    console.log(value);
  }
}