Spotify API Create Temp Playlist Not Loading

Question

I'm making a little app that displays a list of the top first song of an artist's related artists. When I try and load my app for the first time, it shows nothing. But, when I "Reload Application" everything seems to work. When I constantly start "Reloading" it keeps adding more of the same tracks to the list as well.

How do I stop it from continually appending more tracks to the list as well as tighten up the code so that it works on load?

require([
  '$api/models',
  '$views/list#List',
  '$api/toplists#Toplist'

  ], function(models, List, Toplist){
    'use strict';

  // Build playlist
  function buildList(trackURIArray){
    var arr = trackURIArray;
    models.Playlist
      .createTemporary("myTempList")
      .done(function(playlist){ 
        playlist.load("tracks").done(function(loadedPlaylist){
          for(var i = 0; i < arr.length; i++){
            loadedPlaylist.tracks.add(models.Track.fromURI(arr[i]));
          }
        });

        // Create list
        var list = List.forPlaylist(playlist,{
          style:'rounded'
        });

        $('#playlistContainer').append(list.node);
        list.init();
      });
  }

  // Get top track
  function getTopTrack(artist, num, callback){
    var artistTopList = Toplist.forArtist(artist);

    artistTopList.tracks.snapshot(0, num).done(function (snapshot){ 
      snapshot.loadAll('name').done(function(tracks){
        var i, num_toptracks;
        num_toptracks = num; 

        for(i = 0; i < num_toptracks; i++){
          callback(artist, tracks[i]);
        }
      });
    });
  }

  // Get Related
  function getRelated(artist_uri){
    var artist_properties = ['name', 'popularity', 'related', 'uri'];

    models.Artist
    .fromURI(artist_uri)
    .load(artist_properties)
    .done(function (artist){

      artist.related.snapshot().done(function(snapshot){
        snapshot.loadAll('name').done(function(artists){
          var temp = [];

          for(var i = 0; i < artists.length; i++){

            getTopTrack(artists[i], 1, function(artist, toptrack){
              var p, n, u;

              p = artist.popularity;
              n = artist.name;
              u = artist.uri;

              temp.push(toptrack.uri);

            });
          }
          // Build a list of these tracks
          buildList(temp);
        });
      });
    });
  }

  getRelated('spotify:artist:2VAvhf61GgLYmC6C8anyX1');
});

Answer 1

By using Promises you can delay the rendering of the list until you have successfully composed the temporary list with your tracks. Also, in order to prevent the addition of repeated tracks on reload, assign a unique name to your temporary playlist.

require([
  '$api/models',
  '$views/list#List',
  '$api/toplists#Toplist'
], function (models, List, Toplist) {
  'use strict';

  // Build playlist
  function buildList(trackURIArray) {
    var arr = trackURIArray;
    models.Playlist
      .createTemporary("myTempList_" + new Date().getTime())
      .done(function (playlist) {
        playlist.load("tracks").done(function () {
          playlist.tracks.add.apply(playlist.tracks, arr).done(function () {
            // Create list
            var list = List.forCollection(playlist, {
              style: 'rounded'
            });

            $('#playlistContainer').appendChild(list.node);
            list.init();
          });
        });
      });
  }

  // Get top track
  function getTopTrack(artist, num) {
    var promise = new models.Promise();
    var artistTopList = Toplist.forArtist(artist);

    artistTopList.tracks.snapshot(0, num).done(function (snapshot) {
      snapshot.loadAll().done(function (tracks) {
        promise.setDone(tracks[0]);
      }).fail(function (f) {
        promise.setFail(f);
      });
    });

    return promise;
  }

  // Get Related
  function getRelated(artist_uri) {
    models.Artist
      .fromURI(artist_uri)
      .load('related')
      .done(function (artist) {
        artist.related.snapshot().done(function (snapshot) {
          snapshot.loadAll().done(function (artists) {

            var promises = [];

            for (var i = 0; i < artists.length; i++) {
              var promise = getTopTrack(artists[i], 1);
              promises.push(promise);
            }

            models.Promise.join(promises)
              .done(function (tracks) {
                console.log('Loaded all tracks', tracks);
              })
              .fail(function (tracks) {
                console.error('Failed to load at least one track.', tracks);
              })
              .always(function (tracks) {
                // filter out results from failed promises
                buildList(tracks.filter(function(t) {
                  return t !== undefined;
                }));
              });
          });
        });
      });
  }

  getRelated('spotify:artist:2VAvhf61GgLYmC6C8anyX1');
});