基本操作

var a = { name: 'Sam' };
var b = { name: 'Tom' };
var o = {};
o[a] = 1;
o[b] = 2;
console.log(o[a]); // 输出什么？

输出 2, o[a] = 1 => { '[object Object]': 1 }, 同理变成了 2。

const promise1 = Promise.resolve('First');
const promise2 = Promise.resolve('Second');
const promise3 = Promise.reject('Third');
const promise4 = Promise.resolve('Fourth');
const runPromises = async () => {
  const res1 = await Promise.all([promise1, promise2]);
  const res2 = await Promise.all([promise3, promise4]);
  return [res1, res2];
};
runPromises()
  .then((res) => console.log(res))
  .catch((err) => console.log(err));

// Third