窗口滚动到当前元素才显示动画效果

 1 $(function(){
 2     $(window).scroll(function(){
 3         var curr_element = $('当前元素class或id名')
 4         var active_class = '显示动画效果的class或id'
 5         var scroll_h = $(window).scrollTop()+$(window).height();
 6         var self_top = curr_element.offset().top;
 7         var self_h = curr_element.height();
 8         if( (scroll_h > self_top + self_h/2) &&  ( $(window).scrollTop() < self_top + self_h/2) ){
 9             // 显示动画效果
10            curr_element.addClass(active_class);
11         }else{
12            // 退出动画效果
13            curr_element.removeClass(active_class);
14         }
15     })
16 })