src/lay/modules/form.js
function(){
            var top = reElem.offset().top + reElem.outerHeight() + 5 - $win.scrollTop()
            ,dlHeight = dl.outerHeight();
            
            index = select[0].selectedIndex; //获取最新的 selectedIndex
            reElem.addClass(CLASS+'ed');
            dds.removeClass(HIDE);
            nearElem = null;

            //初始选中样式
            dds.eq(index).addClass(THIS).siblings().removeClass(THIS);

            //上下定位识别
            if(top + dlHeight > $win.height() && top >= dlHeight){
              reElem.addClass(CLASS + 'up');
            }
            
            followScroll();
          }
function(){
            var top = reElem.offset().top + reElem.outerHeight() + 5 - $win.scrollTop()
            ,dlHeight = dl.outerHeight();
            
            index = select[0].selectedIndex; //获取最新的 selectedIndex
            reElem.addClass(CLASS+'ed');
            dds.removeClass(HIDE);
            nearElem = null;

            //初始选中样式
            dds.eq(index).addClass(THIS).siblings().removeClass(THIS);

            //上下定位识别
            if(top + dlHeight > $win.height() && top >= dlHeight){
              reElem.addClass(CLASS + 'up');
            }
            
            followScroll();
          }
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