【JavaScript&jQuery】返回顶部

<!doctype html>  
<html>  
    <head>  
        <meta charset="utf-8">  
        <title>返回顶部</title>  
        <meta name="Keywords" content="关键词,关键词">  
        <meta name="Description" content="">  
        <!--css,js-->  
        <style type="text/css">  
            *{margin:0;padding:0;}  
            p{width:300px; height:200px;background:#ccc; margin:10px auto;}  
            .top{width:60px;height:50px;position:fixed;right:22px;bottom:100px;display:none;}  
            .top span{width:60px;height:50px;background:url("img/icon_top.png")no-repeat center #000;display:block;box-shadow:2px 4px 10px #ccc;border-radius:4px;cursor:pointer;}  
        </style>  
        <script type="text/javascript" src="js/jquery.js" ></script>  
    </head>  
    <body>  
        <p>1</p>  
        <p>2</p>  
        <p>3</p>  
        <p>4</p>  
        <p>5</p>  
        <p>6</p>  
        <p>7</p>  
        <div class = "top">  
            <span></span>  
        </div>  
        <script type = "text/javascript">  
            //返回顶部的小图标的现隐  
            $(window).scroll(function(){  
                if($(window).scrollTop() >= 100){  
                    $(".top").fadeIn(600);  
                }else{  
                    $(".top").stop(true,true).fadeOut(600);  
                }  
            });  
            //返回顶部  
            $(".top").click(function(){  
                $("html,body").animate({  
                    scrollTop:0  
                },800);  
            });  
        </script>  
    </body>  
</html>