promise

<div id="box"></div>
<script>
    
    let url01 = "http://api.unclealan.cn:4100/movie/top";
    let url02 = "http://api.unclealan.cn:4100/movie/subject/";
    let url03 = "http://api.unclealan.cn:4100/movie/celebrity/";

    // 获取电影排行榜信息
    function getTopInfo(){
        return new Promise(function(resolve,reject){
            let xhr = new XMLHttpRequest();
            xhr.onload = function(){
                resolve(JSON.parse(xhr.responseText));
            }
            xhr.onerror = function(){
                reject("请求电影排行榜失败");
            }
            xhr.open("GET",url01);
            xhr.send();
        })
    }

    // 获取电影详细信息
    function getMovieInfo(id){
        return new Promise(function(resolve,reject){
            let xhr = new XMLHttpRequest();
            xhr.onload = function(){
                resolve(JSON.parse(xhr.responseText));
            }
            xhr.onerror = function(){
                reject("请求电影详细信息失败");
            }
            xhr.open("GET",url02+id);
            xhr.send();
        })
    }

    // 获取导演信息
    function getDirectorInfo(id){
        return new Promise(function(resolve,reject){
            let xhr = new XMLHttpRequest();
            xhr.onload = function(){
                resolve(JSON.parse(xhr.responseText));
            }
            xhr.onerror = function(){
                reject("请求导演信息失败");
            }
            xhr.open("GET",url03+id);
            xhr.send();
        })
    }

    let message = "排行榜第一的电影是：";
    getTopInfo().then(function(res){
        message += res.subjects[0].title + "<br/>"
        return getMovieInfo(res.subjects[0].id);
    }).then(function(res){
        message += "导演是：" + res.directors[0].name + "<br/>"
        return getDirectorInfo(res.directors[0].id);
    }).then(function(res){
        message += "导演的故乡在：" + res.born_place;
        document.querySelector("#box").innerHTML = message;
    },function(msg){
        console.log(msg);
    })
</script>

<div id="box"></div>
<script>
    
    let url01 = "http://api.unclealan.cn:4100/movie/top";
    let url02 = "http://api.unclealan.cn:4100/movie/subject/";
    let url03 = "http://api.unclealan.cn:4100/movie/celebrity/";

    function getInfo(url,errMes,id=0){
        if(id!==0){
            url += id;
        }

        return new Promise(function(resolve,reject){
            let xhr = new XMLHttpRequest();
            xhr.onload = function(){
                resolve(JSON.parse(xhr.responseText));
            }
            xhr.onerror = function(){
                reject(errMsg);
            }
            xhr.open("GET",url);
            xhr.send();
        })
    }

    let message = "排行榜第一的电影是：";
    getInfo(url01,"获取电影排行榜失败").then(function(res){
        message += res.subjects[0].title;
        return getInfo(url02,"获取电影详情失败",res.subjects[0].id);
    }).then(function(res){
        message += "导演是:"+res.directors[0].name;
        return getInfo(url03,"获取导演失败",res.directors[0].id);
    }).then(function(res){
        message += "导演的故乡:"+res.born_place;
        document.querySelector("#box").innerHTML = message;
    },function(msg){
        console.log(msg);
    })
</script>