function setPrevious() {
    /*
      Initializes the previous index
    */
    var previousIndex = null;
    var previousSong = {};

    /*
      If we are repeating the song, then we just start the song over.
    */
    if (_config2.default.repeat_song) {
      /*
        If the config is shuffled, get the now playing index.
      */
      if (_config2.default.shuffle_on) {
        previousIndex = _config2.default.active_index;
        previousSong = _config2.default.shuffle_list[previousIndex];
      } else {
        previousIndex = _config2.default.active_index;
        previousSong = _config2.default.songs[previousIndex];
      }
    } else {
      /*
        Get the previous index. If the previous index will be less than 0, get the
        last song of the array and continue.
      */
      if (parseInt(_config2.default.active_index) - 1 >= 0) {
        previousIndex = parseInt(_config2.default.active_index - 1);
      } else {
        previousIndex = parseInt(_config2.default.songs.length - 1);
      }

      /*
        If the config is shuffled, we grab the song from the shuffle list
      */
      if (_config2.default.shuffle_on) {
        /*
          Grab song from the shuffle list
        */
        previousSong = _config2.default.shuffle_list[previousIndex];
      } else {
        /*
          Grab song from the songs array
        */
        previousSong = _config2.default.songs[previousIndex];
      }
    }
    /*
      Change the song after the next button has been pressed.
    */
    changeSong(previousSong, previousIndex);

    /*
      Play the newest song.
    */
    _core2.default.play();

    /*
      Sync the play pause elements and run the
      after next callback.
    */
    _playPauseElements2.default.sync();
    _callbacks2.default.run("prev");

    /*
      If we repeated the song, run the repeat song callback.
    */
    if (_config2.default.repeat_song) {
      _callbacks2.default.run("song_repeated");
    }
  }
Sets the previous song on the global songs array.

@access private