javascript - asnyc 中的重复视频持续时间值到 videoId - Youtube API v3

Question

我遇到了异步方法的问题，该方法打印并返回所有 vidDuration 值，然后为每个 videoId 放置 viewCount 值，但 vidDuration 仅重复收到的最后一个值并将其分配给所有 videoId，这显然是错误的。

我尝试在循环中设置一个名为 tempArray 的临时数组，用于存储它所做的每个 vidDuration 值，然后将它们打印到每个 vidDuration ，但话又说回来，它循环遍历输出，但数组中有很多值并复制视频，这是我不想要的。我注释掉了涉及 tempArray 的行并恢复到工作问题。

据我了解，异步方法打印了所有持续时间值，而不转到输出，就好像它卡在那里直到完成并解决，然后它循环 viewCount 并完美输出美好的。我想知道如何以编程逻辑的方式解决这个问题？

脚本:

var channelName = 'ExampleChannel';
var vidWidth = 500;
var vidHeight = 400; 
var vidResults = 15; /* # of videos to show at once - max 50 */
var vidDuration = "";
var viewCount = 0;
var videoId = "";

$(document).ready(function() {
    $.get( // get channel name and load data
        "https://www.googleapis.com/youtube/v3/channels",
        {
            part: 'contentDetails',
            forUsername: channelName,
            key: 'XXXXXXXX'
        },

        function(data)
        {
            $.each(data.items, 
                function(i, item) {
                    console.log(item); // log all items to console
                    var playlistId = item.contentDetails.relatedPlaylists.uploads;
                    getPlaylists(playlistId);

            })
        }         
    );

    // function that gets the playlists
    function getPlaylists(playlistId)
    {
        $.get(
            "https://www.googleapis.com/youtube/v3/playlistItems",
            {
                part: 'snippet',
                maxResults: vidResults,
                playlistId: playlistId,
                key: 'XXXXXXXX'
            },

            // print the results
            function(data)
            {
                var output;
                /*var tempArray = new Array();*/ // temporary array for storing video duration values
                $.each(data.items, 
                    function(i, item) {
                        console.log(item);
                        var vidTitle = item.snippet.title; // video title
                        var vidDesc = item.snippet.description; // video description
                        var videoId = item.snippet.resourceId.videoId; // video id

                        // check if description is empty
                        if(vidDesc == null || vidDesc == "")
                        {
                            vidDesc = "No description was written."; // FIX: test msg to see where it still shows up
                            $('#desc').remove(); // remove video description
                        }
                        else vidDesc = item.snippet.description;

                        getVideoDuration(videoId).done(function(r){
                            vidDuration = r;
                            console.log(r);
                            /*tempArray[i] = r;*/ // store value into each array index
                            /*console.log("Array:", tempArray[i], tempArray);*/ // log to console
                            /*i++;*/ // increment


                        getViewCount(videoId).done(function(r){
                            viewCount = r;
                            console.log(r);

                        //vidDuration = getVideoDuration(videoId);
                        //viewCount = getViewCount(videoId);

                        // temp array index to loop thru array
                        /*$.each(tempArray, function(i){
                            vidDuration = tempArray[i]; // assign index value to vidDuration
                            console.log("In Each vidDuration: ", vidDuration);
                            i++;
                        });*/

                        console.log("id: " + videoId + " duration: " + vidDuration + " viewCount: " + viewCount); // return value in console

                        output = '<li><iframe height="' + vidHeight + '" width="' + vidWidth + '" src=\"//www.youtube.com/embed/' + videoId + '\"></iframe></li><div id="title">' + vidTitle + '</div><div id="desc">' + vidDesc + '</div><div id="duration">Length: ' + vidDuration + '</div><div id="stats">View Count: ' + viewCount + '</div>';

                        // Append results to list tag
                        $('#results').append(output);

                        }); // end of getVideoDuration(videoId).done
                    }); // end of getViewCount(videoId).done
                });
                /*console.log("TEMPARRAY[]",tempArray);*/ // print entire array
            }         
        );
    }

    // return video duration
    function getVideoDuration(videoId) 
    { 
        var defer1 = $.Deferred();
        var r = '';

        $.get(
            "https://www.googleapis.com/youtube/v3/videos",
            {
                part: 'contentDetails',
                id: videoId,
                key: 'XXXXXXXX',
            },

            function(data)
            {
                $.each(data.items,
                    function(i, item) {
                        r = item.contentDetails.duration;
                        defer1.resolve(r);
                        console.log("in vidDuration func", r);
                    });
            }
        );
        return defer1.promise();

    }

    // return video view count
    function getViewCount(videoId) 
    { 
        var defer2 = $.Deferred();
        var r = '';

        $.get(
            "https://www.googleapis.com/youtube/v3/videos",
            {
                part: 'contentDetails, statistics',
                id: videoId,
                key: 'XXXXXXXX',
            },

            function(data)
            {
                $.each(data.items,
                    function(i, item) {
                        r = item.statistics.viewCount;
                        defer2.resolve(r);
                        console.log("in viewCount func", r);
                    });  
            }
        );
        return defer2.promise();
    }
});

截图结果(正常刷新):

屏幕截图结果(使用调试器):

这是使用调试器控制台单步执行时的结果屏幕截图。 (为什么结果与页面正常加载时不同？这是异步方法的典型操作吗？我该如何解决这个问题？)

Answer 1

事实上，第二个 Promise 放错了位置，第二个 Promise 在第一个 Promise 的所有 Promise 都已解决之后得到解决，因此最后一个值被保存。逻辑性

现在，如果您解决了第一个 promise 何时，第二个 promise 得到了逐一解决，您就能够纠正问题。

var view = 0;
r = item.contentDetails.duration; // video duration 
getViewCount(videoId).done(function(t){
        view = t;
        dfrd1.resolve(r, view);
});

查看截图:

我稍微改变了代码来解决这个问题。

var channelName = 'example';
var vidWidth = 500;
var vidHeight = 400; 
var vidResults = 15; /* # of videos to show at once - max 50 */
var vidDuration = "";
var viewCount = 0;
var videoId = "";

$(document).ready(function() {
    $.get( // get channel name and load data
        "https://www.googleapis.com/youtube/v3/channels",
        {
            part: 'contentDetails',
            forUsername: channelName,
            key: 'xxx'
        },

        function(data)
        {
            $.each(data.items, 
                function(i, item) {
                    //console.log(item); // log all items to console
                    var playlistId = item.contentDetails.relatedPlaylists.uploads;
                    //var viewCount = console.log(item.statistics.viewCount);
                    getPlaylists(playlistId);

            });
        }         
    );

    // function that gets the playlists
    function getPlaylists(playlistId)
    {
        $.get(
            "https://www.googleapis.com/youtube/v3/playlistItems",
            {
                part: 'snippet',
                maxResults: vidResults,
                playlistId: playlistId,
                key: 'xxx'
            },

            // print the results
            function(data)
            {
                var output;
                $.each(data.items, 
                    function(i, item) {
                        console.log(item);
                        var vidTitle = item.snippet.title; // video title
                        var vidDesc = item.snippet.description; // video description
                        var videoId = item.snippet.resourceId.videoId; // video id

                        // check if description is empty
                        if(vidDesc == null || vidDesc == "")
                        {
                            vidDesc = "No description was written."; // FIX: test msg to see where it still shows up
                            $('#desc').remove(); // remove video description
                        }
                        else vidDesc = item.snippet.description;

                        getVideoDuration(videoId).done(function(d, v){
                             vidDuration = d;
                             //console.log(r);


                               viewCount = v;

                        document.write("id: " + videoId + " duration: " + vidDuration + " viewCount: " + viewCount); // return value in console

                        document.write("<br>");

                        output = '<li><iframe height="' + vidHeight + '" width="' + vidWidth + '" src=\"//www.youtube.com/embed/' + videoId + '\"></iframe></li><div id="title">' + vidTitle + '</div><div id="desc">' + vidDesc + '</div><div id="duration">Length: ' + vidDuration + '</div><div id="stats">View Count: ' + viewCount + '</div>';

                    // Append results to list tag
                    $('#results').append(output);
                   });
                });
            }         
        );
    }

    // return video duration
    function getVideoDuration(videoId) 
    { 
        var dfrd1 = $.Deferred();
        var r = '';
        $.get(
            "https://www.googleapis.com/youtube/v3/videos",
            {
                part: 'contentDetails',
                id: videoId,
                key: 'xxx',
            },

            function(data)
            {
                $.each(data.items,
                    function(i, item) {
                        //videoId = item.snippet.resourceId.videoId;
                        var view = 0;
                        r = item.contentDetails.duration; // video duration 
                        getViewCount(videoId).done(function(t){
                          view = t;
                          dfrd1.resolve(r, view);
                        });

                        //alert(videoId);
                    });    
            }
        );
        return dfrd1.promise();
    }

    // return video view count
    function getViewCount(videoId) 
    { 
        var dfrd2 = $.Deferred();
        var r = '';
        $.get(
            "https://www.googleapis.com/youtube/v3/videos",
            {
                part: 'contentDetails, statistics',
                id: videoId,
                key: 'xxx',
            },

            function(data)
            {

                $.each(data.items,
                    function(i, item) {
                        //videoId = item.snippet.resourceId.videoId;

                        r = item.statistics.viewCount; // view count
                        //alert(videoId);
                        dfrd2.resolve(r);

                      // console.log("in", r);
                    });  
            }
        );
        return dfrd2.promise();
    } 
});