loadBgms(bgms, type) {
      bgms.forEach(bgm => {
        const item = $('.factory .track')
          .clone()
          .appendTo('.music-list')
          .attr('bgm-type', type)
          .attr('bgm-id', bgm.api_id);

        $('.id', item).text('#' + String(bgm.api_id).pad(3, '0'));
        $('.desc', item).text(bgm.api_name || "");
      });

      this.initTrackListeners();
    }
Adds elements with information of tracks in current type to cleared list container.
@param {Array} bgms - list of bgm, with `api_id` and `api_name`.
@param {String} type - type name of bgm path, acceptable: `port`, `battle` and `fanfare`.