场景：啰嗦的妻子
丈夫和妻子去看电影，排队时，妻子却说自己饿了，去便利店买东西；
- Promise 实现
console.log('person1: show ticket')
console.log('person2: show ticket')
console.log('husband: let go in')
console.log('wife:no, i am hungry')
const getBread = new Promise((resolve,reject) => {
setTimeout(()=>{
resolve('bread')
},1000)
})
const getButter = getBread.then((bread)=> {
console.log(`husband: here is ${bread},let us go in`)
console.log(`wife: no, i need some butter`)
return new Promise((resolve,reject) => {
setTimeout(()=>{
resolve('butter')
},1000)
})
})
const getDrink = getButter.then(butter => {
console.log(`husband: here is ${butter},let us go in`)
console.log(`wife: no, i need some drink`)
return new Promise((resolve,reject) => {
setTimeout(()=>{
resolve('drink')
},1000)
})
})
getDrink.then(resolve => {
console.log(resolve);
console.log('person3: show ticket')
})
console.log('person4: show ticket')
console.log('person5: show ticket')
- 运行结果
person1: show ticket
VM44:2 person2: show ticket
VM44:3 husband: let go in
VM44:4 wife:no, i am hungry
VM44:29 person4: show ticket
VM44:30 person5: show ticket
VM44:10 husband: here is bread,let us go in
VM44:11 wife: no, i need some butter
VM44:18 husband: here is butter,let us go in
VM44:19 wife: no, i need some drink
VM44:26 drink
VM44:27 person3: show ticket
- async await 实现
console.log('person1: show ticket')
console.log('person2: show ticket')
const getBread = new Promise((resolve,reject) => {
setTimeout(()=>{
resolve('bread')
},1000)
})
// async 函数 return 的为一个 promise 对象
// 异步操作的结果需要放在 promise 对象里
const getButter = async () => {
return await new Promise((resolve,reject) => {
setTimeout(()=>{
resolve('butter')
},1000)
})
}
const getDrink = new Promise((resolve,reject) => {
setTimeout(()=>{
resolve('drink')
},1000)
})
const goIn = async () => {
console.log('husband: let go in')
console.log('wife:no, i am hungry')
let bread = await getBread;
console.log(`husband: here is ${bread},let us go in`)
console.log(`wife: no, i need some butter`)
let butter = await getButter()
console.log(`husband: here is ${butter},let us go in`)
console.log(`wife: no, i need some drink`)
let drink = await getDrink
console.log(`husband: here is ${drink},let us go`)
console.log('wife: all right')
}
goIn();
console.log('person4: show ticket')
console.log('person5: show ticket')
