利用Promise实现Promise.all

let pall = function(...args){
    let Res = []
    let Err = []
    return new Promise((resolve,reject)=>{
        for(let i=0;i<args.length;i++){
            args[i].then(res=>{
                Res.push(res)
                if(Res.length == args.length){
                    resolve(Res)
                }
            }).catch(err=>{
                Err.push(err)
                reject(Err)
            })
        }
    })
}

let p1 = new Promise((resolve,reject)=>{
    setTimeout(()=>{    
        resolve("p1")
    },1000)
    
})
let p2 = new Promise((resolve,reject)=>{
    setTimeout(()=>{    
        resolve("p2")
    },500)
})

pall(p1,p2).then(res=>{
    console.log(res)
}).catch(err=>console.log(err))