同步执行

Promise 与async

var p1=new Promise((resolve,reject)=>{
        setTimeout(()=>{console.log("first");resolve()},1000)
    })
    var p2=new Promise((resolve,reject)=>{
        setTimeout(()=>{console.log("two");resolve()},2000)
    })
    var p3=Promise.all([p1,p2])
    p3.then((res)=>{
        console.log('over')
        setTimeout(()=>{ console.log(res+" two")},1000)
       
    })
    请求p1,p2，都结束后执行请求p3

    async function add(a){
       let p1=await  new Promise((resolve,reject)=>{setTimeout(()=>{console.log(a);resolve(a)},1000)})
        return p1
    }
    add('kal').then((res)=>{ setTimeout(()=>{console.log(res+'rese')},1000) })
    

请求结束后执行then ()