Question

链式调用异步函数。

循环遍历包含异步事件的函数数组，每次异步事件完成后调用 next 。

const chainAsync = fns => {
  let curr = 0;
  const next = () => fns[curr++](next);
  next();
};

chainAsync([
  next => {
    console.log('0 seconds');
    setTimeout(next, 1000);
  },
  next => {
    console.log('1 second');
  }
]);