使用 for await ...of 实现倒计时功能

forAwaitOf.js

// 在线 demo: https://repl.it/@phobal/forAwaitOf#index.js

let i = 60;

const items = Array(i)
  .fill()
  .map((_, i) => (i + 1) * 1000);

function somethingAsync(time) {
  return delay(time).then(() => Promise.resolve(i--));
}

function delay(time) {
  return new Promise(resolve => {
    setTimeout(resolve, time);
  });
}

(async () => {
//   const promises = await Promise.all(items.map(e => somethingAsync(e)));
//   for (const res of promises) {
//     console.log(res);
//   }

  i = 60; //reset counter

  for await (const res of items.map(e => somethingAsync(e))) {
    console.log(res);
  }
})();