// promise方法
let p1 = new Promise((resolve,reject) => {
setTimeout(() => {
resolve('我是p1')
},4000)
})
let p2 = new Promise((resolve,reject) => {
setTimeout(() => {
resolve('我是p2')
},200)
})
let p3 = new Promise((resolve,reject) => {
setTimeout(() => {
resolve('我是p3')
},200)
})
// 想讓p1完成後再執行P2再執行P3
// 數量太多隻能循環嵌套
p1.then((res) => {
console.log(res);
p2.then((res) => {
console.log(res);
p3.then((res) => {
console.log(res);
})
})
})
// async await語法糖
let a1=()=>{
return new Promise((resolve,reject) => {
setTimeout(() => {
resolve('我是a1')
},4000)
})
}
let a2=()=>{
return new Promise((resolve,reject) => {
setTimeout(() => {
resolve('我是a2')
},40)
})
}
let a3=()=>{
return new Promise((resolve,reject) => {
setTimeout(() => {
resolve('我是a3')
},40)
})
}
// 想讓a1完成後再執行a2再執行a3
//能避免回調
async function asy(){
await a1().then((res) => {console.log(res)});
await a2().then((res) => {console.log(res)});;
await a3().then((res) => {console.log(res)});;
}
asy();
一眼看懂promise與async await的區別
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