code: function buildNextItem(iscontrol) {
          if ($body.classList.contains('overview')) {
              return false;
          }
          $curSlide = $slides[curIndex];
          var subBuilded = toArray($('.building'), $curSlide);
          var list;
          if (subBuilded.length) {
  
              while (list = subBuilded.shift()) {
                  list = list.classList
                  list.remove('building');
                  list.add('builded');
              }
          }
          var toBuild = $('.tobuild', $curSlide);
  
          if (!toBuild.length) {
              return false;
          }
  
          var item = toBuild.item(0);
          !iscontrol && $B.fire('slide do build', {
              slideID: curIndex,
              direction: 'next',
              build: item.dataset.index
          })
          list = item.classList;
  
          $B.fire('slide.update', curIndex | 0, (item.dataset.index | 0) + 1, 'next');
          list.remove('tobuild');
  
          if (list.contains('subSlide')) {
              toArray($('.subSlide.builded', $curSlide)).forEach(function($item) {
                  $item.classList.add('subBuilded');
              });
          }
  
          list.add('building');
          return true;
      }
docs: 单行前进