Spotify Apps API 1.x: Printing player positions after changing track

spotify-apps-api-printing-position

    require(["$api/models"], function(models) {

      var getPosition = function(callback) {
        models.player.load("position")
        .done(function(player) {
          callback(null, player.position);
        })
        .fail(function(error) {
          callback(error);
        });
      };

      var changeTrack = function(uri, callback) {
        console.log("Changing track to " + uri);
        models.player.playTrack(models.Track.fromURI(uri))
        .done(function() {
          callback();
        })
        .fail(function(error) {
          callback(error);
        });
      }

      var handleError = function(error) {
        if (error) {
          throw new Error("An error occurred while loading the position", error);
        }
      };

      var handleChange = function(event) {
        printPosition();
      };

      var printPosition = function(callback) {
        getPosition(function(error, position) {
          handleError(error);
          console.log("The current position is " + models.player.position);
          if (callback) {
            callback();
          }
        });
      };

      var printCurrentlyPlayingTrack = function(callback) {
        models.player.load("track")
        .done(function(player) {
          console.log("Currently playing track is " + models.player.track.uri);
          callback();
        })
        .fail(function(error) {
          callback(error);
        });
      };

      var printInitial = function(callback) {
        printCurrentlyPlayingTrack(function() {
          printPosition(function() {
            callback();
          });
        });
      };

      models.player.addEventListener('change', handleChange);

      // Print the initial position
      printInitial(function() {

        // Change to a different track -- The event listener will print the new position
        var trackUri = "spotify:track:27H6Luq76clxdaGT5iZH0m";
        changeTrack(trackUri, function(error) {
          handleError(error);
          console.log("Changed track");

            // Reset track -- The event listener will print the new position
            var someOtherTrackUri = "spotify:track:5hxDTiXcMrDC6HluDvotfj";
            changeTrack(someOtherTrackUri, function(error) {
              handleError(error);
              console.log("Reset track");
            });
        });
      });

    });