await promise.all（）和multiple await有什么区别吗？

Question

const [result1, result2] = await Promise.all([task1(), task2()]);

const t1 = task1();
const t2 = task2();

const result1 = await t1;
const result2 = await t2;

和

const [t1, t2] = [task1(), task2()];
const [result1, result2] = [await t1, await t2];

Answer 1

注：

这个答案只涵盖awaitin series和promise.all之间的时间差异。一定要阅读@mikep的全面回答，它还涵盖了错误处理中更重要的区别。

为了回答这个问题，我将使用一些示例方法：

null

const data = await Promise.all([res(3000), res(2000), res(1000)])
//                              ^^^^^^^^^  ^^^^^^^^^  ^^^^^^^^^
//                               delay 1    delay 2    delay 3
//
// ms ------1---------2---------3
// =============================O delay 1
// ===================O           delay 2
// =========O                     delay 3
//
// =============================O Promise.all

async function example() {
  const start = Date.now()
  let i = 0
  function res(n) {
    const id = ++i
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        resolve()
        console.log(`res #${id} called after ${n} milliseconds`, Date.now() - start)
      }, n)
    })
  }

  const data = await Promise.all([res(3000), res(2000), res(1000)])
  console.log(`Promise.all finished`, Date.now() - start)
}

example()