javascript - 为什么 promise 同时有效？

Question

new Promise((resolve, reject) => {

  setTimeout(function() {
    console.log(1)
    resolve()
  }, 200)
  
}).then(new Promise((resolve, reject) => {

  setTimeout(function() {
    console.log(2)
    resolve()
  }, 0)
  
}))

为什么这个输出是 2 1，而不是 1 2？promise 应该按顺序做事？为什么会这样

Answer 1

then 的第一个参数是回调函数。引用 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then .

new Promise((resolve, reject) => {
    setTimeout(function () {
        console.log(1)
        resolve()
    }, 200)
}).then(() => {
    return new Promise((resolve, reject) => {
      setTimeout(function () {
         console.log(2);
         resolve();
    }, 0)});
});