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一个关于宏任务微任务的题目，你"绝对"猜不到答案

 2 years ago
source link: https://zhuanlan.zhihu.com/p/449183802
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一个关于宏任务微任务的题目，你"绝对"猜不到答案

在饥人谷学前端、Java、C++。 咨询见个人简介

这是一个关于Promise 微任务的题目，猜猜以下代码输出是什么？为什么？ 

let p1 = Promise.resolve()
  .then(v => console.log(1))
  .then(v => console.log(2))
  .then(v => console.log(3))
 
p1.then(v => console.log(4))
p1.then(v => console.log(5))
 
let p2 = Promise.resolve()
  .then(v => console.log(11))
  .then(v => console.log(22))
  .then(v => console.log(33))
 
p2.then(v => console.log(44))
p2.then(v => console.log(55))

上面的题目发散自一个大厂的面试题

async function async1() {
  console.log('async1 start');
  await async2();
  console.log('async1 end');
}
async function async2() {
  console.log('async2 start');
  return new Promise((resolve, reject) => {
 resolve();
 console.log('async2 promise');
  })
}
console.log('script start');
setTimeout(function() {
  console.log('setTimeout');
}, 0);  
async1();
new Promise(function(resolve) {
  console.log('promise1');
  resolve();
}).then(function() {
  console.log('promise2');
}).then(function() {
  console.log('promise3');
});
console.log('script end')

可以在评论区或者 https://xiedaimala.com/bbs/topics/570#/ 晒自己的解题思路。如果需要，我也可以写篇文章细细讲解。点


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