2022.06.11

1. 执行顺序题

   第一题

   ```javascript let obj = { num1: 117 } let res = obj; obj.child = obj = { num2: 935 }; var x = y = res.child.num2; console.log(obj.child); console.log(res.num1); console.log(y);

// undefined // 117 // 935

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### 第二题
```javascript
async function async1(){
    console.log('async1 start')
    await async2()
    console.log('async1 end')
}
async function async2(){
    console.log('async2')
}
console.log('script start')
setTimeout(function(){
    console.log('setTimeout')
},0)
async1()
new Promise((resolve)=>{
    console.log('promise1')
    resolve()
}).then(function (){
    console.log('promise2')
})
console.log('script end')
// script start
// async1 start
// async2
// promise1
// script end
// async1 end
// promise2
// setTimeout

第三题

Promise.resolve().then(()=>{ 
        console.log('第一个回调函数：微任务1') 
        setTimeout(()=>{ console.log('第三个回调函数：宏任务2') },0) 
}) 
setTimeout(()=>{ 
    console.log('第二个回调函数：宏任务1') 
    Promise.resolve().then(()=>{ console.log('第四个回调函数：微任务2') }) 
},0)
// 微任务1
// 宏任务1
// 微任务2
// 宏任务2

第四题

console.log("start");
async function async1() {
  console.log("async1 start");
  await async2();
  console.log("async2 end");
  await async3();
  console.log("async3 end");
}
function async2() {
  console.log("async");
}
function async3() {
  console.log("async3 start");
}
console.log("scrpit start");
setTimeout(() => {
  console.log("setTimeOut");
}, 0);
async1();
new Promise(function (reslove) {
  console.log("promise1");
  reslove("promise2");
}).then((res) => {
  console.log(res);
});
console.log("script end");
// start
// script start
// async1 start
// async
// promise1
// script end
// async1 end
// async3 start
// promise2
// async3 end 
// setTimeout

第五题

let promiseFunc = function () {
  return new Promise((resolve, reject) => {
    console.log(this.name);
    setTimeout(function () {
      console.log(this.name);
      console.log('abc');
      resolve('cba');
    }, 2000);
    console.log('aaa');
  });
};
let Object1 = {
  name: 'james',
  func: promiseFunc,
};
Object1.func().then((result) => {
  console.log('result', result);
});
// james
// aaa
// undefied(箭头函数的this向上查找到第一个函数作用域，Promise的回调函数的this没有name)
// abc
                  // resolve（cbd）后执行then
// result，cbd

第六题

console.log('start here');
const foo = () => {
  return new Promise((resolve, reject) => {
    console.log('first promise constructor');
    let promise1 = new Promise((resolve, reject) => {
      console.log('second promise constructor');
      setTimeout(() => {
        console.log('setTimeout here');
        // 这里的resolve会触发哪里的then，还是说不触发
        resolve();
      }, 0);
      resolve('promise1');
    });
    resolve('promise0');
    promise1.then((arg) => {
      console.log(arg);
    });
  });
};
foo().then((arg) => {
  console.log(arg);
});
console.log('end here');
// start here
// fisrt
// second
// end here
// promise1
// promise0
// setTimeout here

第七题

console.log('Script开始')
setTimeout(() => {
  console.log('第一个回调函数，宏任务1')
  Promise.resolve().then(function() {
    console.log('第四个回调函数，微任务2')
  })
}, 0)
setTimeout(() => {
  console.log('第二个回调函数，宏任务2')
  Promise.resolve().then(function() {
    console.log('第五个回调函数，微任务3')
  })
}, 0)
Promise.resolve().then(function() {
  console.log('第三个回调函数，微任务1')
})
console.log('Script结束')
// script开始
// script结束
// 微任务1
// 宏任务1
// 宏任务2
// 微任务2
// 微任务3

第八题

console.log('Script开始')
setTimeout(() => {
  console.log('宏任务1（setTimeout)')
  Promise.resolve().then(() => {
    console.log('微任务promise2')
  })
}, 0)
setImmediate(() => {
  console.log('宏任务2')
})
setTimeout(() => {
  console.log('宏任务3（setTimeout)')
}, 0)
console.log('Script结束')
Promise.resolve().then(() => {
  console.log('微任务promise1')
})
process.nextTick(() => {
  console.log('微任务nextTick')
})
// script开始
// script结束
// 个人错误答案
    // 微任务1
    // 微任务NextTick
// 微任务nectTick
// 微任务1
// 宏2 setImmediate
// 宏1
// promise2
// 宏3

第九题

async function async1 () {
  console.log('async1 start');
  await new Promise(resolve => {
    console.log('promise1')
    resolve('promise1 resolve')
  }).then(res => console.log(res))
  console.log('async1 success');
  return 'async1 end'
}
console.log('srcipt start')
async1().then(res => console.log(res))
console.log('srcipt end')
// script start
// async1 start
// promise1
// script end
// promise1 resolve
// async1 success
// async1 end

算法