code: function(element, move, property){
              var scrollKeys = property === 'translateY'
                  ? ['scrollTop', 'offsetHeight', 'scrollHeight']
                  : property === 'translateX' ? ['scrollLeft', 'offsetWidth', 'scrollWidth'] : null;
              if(!scrollKeys){return ''}
  
              var scroll_start = element[scrollKeys[0]] || 0;
              if(scroll_start === 0 && move >= 0){
                  return 'start'
              }
              var visible_range = element[scrollKeys[1]] || 0,
                  scroll_range = element[scrollKeys[2]] || 0;
              if(scroll_range === visible_range + scroll_start){
                  return 'end'
              }
              return 'middle'
          }
docs: 根据滑动方向判断
  @param element 具有scroll的DOM
  @param move 滚动的距离
  @param property 滚动的方向
  @returns {*} 返回当前滑动状态下，element元素的scroll位置信息，'middle'-scroll正在滚动
  @private