串行Promise的实现

[jindada]

const data = [1, 2, 3, 4, 5];

const request = item => new Promise(resolve => 
  setTimeout(() => {
     console.log(item);
     resolve(item);
  }, 2000)
);

const queue = async data => {
  let result = [];
  for (let item of data) {
     result.push(await request(item));
  }
  return await result;
};

queue(data).then(data => console.log('结束', data));