返回顶部按钮功能的实现

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>toTop</title>
<style type="text/css">
*{
    margin:0;
    padding: 0;
}
html{
    height: 100%;
}
.toTopBtn{
    position: fixed;
    bottom: 100px;
    right: 100px;
    background: #333;
    color: #fff;
    padding: 5px 10px;
    cursor: pointer;
    display: none;
}
</style>
</head>
<body>
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<script type="text/javascript" src="http://vscss.com/dm/jquery.js"></script>
<script type="text/javascript">
$(function(){
    var toTop = $("<span class=\'toTopBtn\'>返回顶部</span>");
    $(\'body\').append(toTop);
    $(window).scroll(function(event) {
        if($(window).scrollTop()>100){
            $(\'.toTopBtn\').fadeIn();
        }else{
            $(\'.toTopBtn\').fadeOut();
        }
    });
    $(\'.toTopBtn\').click(function(){
        $(\'html,body\').animate({
            scrollTop:0
        },200);
        //return false;
    });
});
</script>
</body>
</html>