<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>返回顶部</title> <script src="scripts/jquery-1.7.1.min.js"></script> </head> <body> <script type="text/javascript"> $(function(){ var toppos = 0; $(".back_top_index").hide(); $(document).scroll( function(){ toppos=$(document).scrollTop(); var oClient =$(window).height();//当前窗口可视区域高度 if(toppos>oClient){ $(".back_top_index").fadeIn(); }else if(toppos==0){ $(".back_top_index").fadeOut(); } } ) $(".back_top_index").click(function(){ $("html,body").animate({scrollTop:0}) }) }) </script> <div style="height:2000px;">3423424</div> <div class="back_top_index">1</div> <style> .back_top_index{width: 50px;height: 50px;position: fixed;bottom: 10px;right: 10px;background-color: red;} </style> </body> </html>