Promise.all

Promise.all

function promeseA (){
   return new Premise((resole,reject)=>{
       setTimeout(()=>{
        console.log('A')
        resole('A')
      },1000)
     
   })
}
function promeseB (){
   return new Premise((resole,reject)=>{
     setTimeout(()=>{
        resole('B')
      },3000)
     
   })
}

Promise.all().then(resole=>{
console.log('Promise.all',resole);
})

最终返回的结果
//“[object Array] (2) [“A”,”B”]