js返回顶部小Demo

    <style>

        .divH {

            height: 1800px;

        }

        .divT {

            width: 50px;

            height: 50px;

            font-size: 18px;

            background-color: #2F4F4F;

            text-align: center;

            color: white;

            position: fixed;

            right: 18px;

            bottom: 18px;

        }

        .divT:hover{

            cursor: pointer;

        }

        .hide {

            display: none;

        }

    </style>

</head>

<body>

<div class="divH"></div>

<div class="divT hide" onclick="ReturnTop();"><strong>返回顶部</strong></div>

<script src="./jq/jquery-1.9.1.min.js"></script>

<script>

    window.onscroll = function () {

        var current = $(window).scrollTop();

        if (current > 180){

            $(".divT").removeClass("hide");

        }else {

            $(".divT").addClass("hide");

        }

    };

    function ReturnTop() {

        $(window).scrollTop(0);

    }

</script>
网页右下角有个返回顶部按钮，模仿淘宝？window.scrollTop()方法