很多的网站上都有返回顶部功能,判断滚动参数动态显示与隐藏,比较适合初学者
- <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
- <html xmlns="http://www.w3.org/1999/xhtml">
- <head>
- <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
- <title>实现动态的显示回到顶部与否</title>
- <style>
- /*返回顶部*/
- .back_top {width:45px;height:45px;background:url(back_top_new.png) 0 0;position:fixed;left:50%;margin-left:500px;bottom:105px;display:none;}
- .back_top:hover{background:url(images/back_top_new.png) 0 -46px;}
- </style>
- </head>
- <body>
- <a title="返回顶部" href="javascript:void(0)" class="back_top"></a>
- <script src="js/jquery-1.11.0.min.js"></script>
- <script>
- var mousewheelevt=(/Firefox/i.test(navigator.userAgent))? "DOMMouseScroll" : "mousewheel"; //FF doesn't recognize mousewheel as of FF3.x
- if (document.attachEvent) //if IE (and Opera depending on user setting)
- document.attachEvent("on"+mousewheelevt, function(e){
- var t=document.body.scrollTop+document.documentElement.scrollTop;
- if(t==0){
- $(".back_top").css("display","none");
- }
- else{
- $(".back_top").css("display","block");
- }
- });
- else if (document.addEventListener) //WC3 browsers
- document.addEventListener(mousewheelevt, function(e){
- var t=document.body.scrollTop+document.documentElement.scrollTop;
- if(t==0){
- $(".back_top").css("display","none");
- }
- else{
- $(".back_top").css("display","block");
- }
- }, false);
- </script>
- </body>
- </html>
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