12.promise-ajax

.html

 <script>
        http("top/playlist/?cat=华语").then(res=>{
            let id=res.playlists[0].id;
            return id;
        }).then(res=>{
            let id=res;
            http(`playlist/detail?id=${id}`).then(res=>{
                var {name,id}=res.playlist.tracks[0]
                console.log(id);
            })
        })
    </script>

index.js

function http(url){
    return new Promise((resolve,reject)=>{
        $.ajax({
            url:`http://192.168.4.18:3000/${url}`,
            type:"get",
            success:res=>{
                resolve(res)
            },
            error:err=>{
                reject(err)
            }
        })
    })
}