// 题目一
let obj = {
num1: 117
}
let res = obj;
obj.child = obj = {
num2: 935
};
var x = y = res.child.num2;
console.log(obj.child); // undefined
console.log(res.num1); // 117
console.log(y); // 935
/**注意点：
* 1、虽然 = = 是右执行再到左执行，但是获取属性的优先级比赋值操作更高。
* 2、引用类型，注意存储的是地址
* 解释：
* {num1: 117}为地址aaa
* obj指向aaa，res指向aaa
* obj.child ，即地址aaa下增加child变量 ，即地址aaa处的值变成 {num1: 117,child:{num2: 935}}
* obj = { num2: 935 }; { num2: 935 } 为地址bbb,改变obj指向为bbb
* 而此刻res指向aaa，obj指向为bbb，故res的值为{num1: 117,child:{num2: 935}}，obj的值为{ num2: 935 }
*/
// 题目二
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')
/**注意await那行代码会立即执行
* script start
* async1 start
* async2
* promise1
* script end
* async1 end
* promise2
* setTimeout
*/
// 题目三
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)
/**
* 第一个回调函数：微任务1
* 第二个回调函数：宏任务1
* 第四个回调函数：微任务2
* 第三个回调函数：宏任务2
*/
// 题目四
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
* scrpit start
* async1 start
* async
* promise1
* script end
* async2 end
* async3 start
* promise2
* async3 end
* setTimeOut
*/
// 题目五
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
* undefined setTimeout 中的 this 默认指向 window
* abc
* result cba
*/
// 题目六
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');
resolve();
}, 0);
resolve('promise1');
});
resolve('promise0');
promise1.then((arg) => {
console.log(arg);
});
});
};
foo().then((arg) => {
console.log(arg);
});
console.log('end here');
/**
* start here
* first promise constructor//Promise构造函数的参数里面，这其实是同步代码
* second promise constructor
* end here
* -------第一轮宏任务结束-------
* promise0❌ promise1
* setTimeout here promise0
* promise1 setTimeout here
*/
// 题目七
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
* -------第一轮宏任务结束-------
* 第三个回调函数，微任务1
* -------第一轮微任务结束-------
* 第一个回调函数，宏任务1
* -------第二轮宏任务结束-------
* 第四个回调函数，微任务2
* -------第二轮微任务结束-------
* 第二个回调函数，宏任务2
* -------第三轮宏任务结束-------
* 第五个回调函数，微任务3
* -------第三轮微任务结束-------
*/
// 题目八
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')
})
/**在一个异步流程里，setImmediate会比定时器setTimeout先执行，
* process.nextTick()是一个特殊的异步API，他不属于任何的Event Loop阶段。事实上Node在遇到这个API时，Event Loop根本就不会继续进行，会马上停下来执行process.nextTick()，这个执行完后才会继续Event Loop
* Script开始
* Script结束
* 微任务nextTick
* 微任务promise1
* 宏任务2
* 宏任务1（setTimeout
* 微任务promise2
* 宏任务3（setTimeout
*/
// 题目九
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')
/**
* srcipt start
* async1 start
* promise1
* srcipt end
* promise1 resolve
* async1 success
* async1 end
*/
// Promise执行相关
// 题目一
Promise.reject('err!!!')
.then((res) => {
console.log('success', res)
}, (err) => {
console.log('error', err)
}).catch(err => {
console.log('catch', err)
})
/**
* error err!!!
*/
// 题目二
Promise.resolve()
.then(function success (res) {
throw new Error('error!!!')
}, function fail1 (err) {
console.log('fail1', err)
}).catch(function fail2 (err) {
console.log('fail2', err)
})
/**
* resolve改变Promise状态为fulfilled ==> throw new Error('error!!!') ==> 进入catch
* fail2 Error: error!!!
*/
// 题目三
Promise.resolve('1')
.then(res => {
console.log(res)
})
.finally(() => {
console.log('finally')
})
Promise.resolve('2')
.finally(() => {
console.log('finally2')
return '我是finally2返回的值'
})
.then(res => {
console.log('finally2后面的then函数', res)
})
/**
* 1
* finally❌ finally2
* finally2 finally
* finally2后面的then函数 2
*/
// 题目四
function promise1 () {
let p = new Promise((resolve) => {
console.log('promise1');
resolve('1')
})
return p;
}
function promise2 () {
return new Promise((resolve, reject) => {
reject('error')
})
}
promise1()
.then(res => console.log(res))
.catch(err => console.log(err))
.finally(() => console.log('finally1'))
promise2()
.then(res => console.log(res))
.catch(err => console.log(err))
.finally(() => console.log('finally2'))
/**
* promise1
* 1
* error
* finally1
* finally2
*/
// 题目五
async function async1 () {
try {
await Promise.reject('error!!!')
} catch(e) {
console.log(e)
}
console.log('async1');
return Promise.resolve('async1 success')
}
async1().then(res => console.log(res))
console.log('script start')
/**
* script start
* error!!!
* async1
* async1 success
*/
// 题目六
const p1 = new Promise((resolve) => {
setTimeout(() => {
resolve('resolve3');
console.log('timer1')
}, 0)
resolve('resovle1');
resolve('resolve2');
}).then(res => {
console.log(res)
setTimeout(() => {
console.log(p1)
}, 1000)
}).finally(res => {
console.log('finally', res)
})
// 还想做多一点：https://juejin.cn/post/6844904077537574919#heading-49
/**
* resovle1
* finally ❌ finally undefined
* timer1
*/