code: function(event) {
        var self = this;
  
        if (self._queue.length > 0) {
          var task = self._queue[0];
  
          // Remove this task if a matching event was passed.
          if (task.event === event) {
            self._queue.shift();
            self._loadQueue();
          }
  
          // Run the task if no event type is passed.
          if (!event) {
            task.action();
          }
        }
  
        return self;
      }
docs: Queue of actions initiated before the sound has loaded.
  These will be called in sequence, with the next only firing
  after the previous has finished executing (even if async like play).
  @return {Howl}