<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
</body>
<script>
//模拟异步请求
let p1 = new Promise((resolve,reject) => {
setTimeout(() => {
resolve("p2 Promise模拟数据请求已返回")
}, 1000);
})
//模拟异步请求
let p2 = new Promise((resolve,reject) => {
setTimeout(() => {
resolve("p2 Promise模拟数据请求已返回")
}, 2000);
})
console.time("cost")
// promise all使用
Promise.all([p1,p2]).then(res => {
console.log(res)//每个p都有resolve返回时，才会执行promise all，res才会出来
console.timeEnd("cost")//记录花费的时间
})
// 手写promsie all原理
function allSelf(arr){
return new Promise((resolve,reject) => {
let resArr = []
for(let i in arr){
Promise.resolve(arr[i])
.then(res => {
resArr[i] = res
if(resArr.length == arr.length){
resolve(resArr)
}
}).catch(err => {
reject(err)
})
}
})
}
//调用自己手写的promise all原理
console.time("cost")
allSelf([p1,p2]).then(res => {
console.log(res)
console.timeEnd("cost")//记录花费的时间
})
</script>
</html>版权声明：本文为A186G原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接和本声明。