html-滚动到底部自动加载

DOCTYPE html>
html>
head>
    title>无限翻页测试title>
    meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    script src="http://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js">script>
    style type="text/css">
    #spinner{
        position: fixed;
        top: 20px;
        left: 40%;
        display: block;
        color: red;
        font-weight: 900;
        background-color: rgba(80, 80, 90, 0.22);
        padding-top: 20px;
        padding-bottom: 20px;
        padding-left: 100px;
        padding-right: 100px;
        border-radius: 15px;
    }
    style>
head>
body>
    div id="sample">
    div>
    div id="spinner">
        正在加载
    div>
    script type="text/javascript">
        var index = 0;
        function lowEnough(){
            var pageHeight = Math.max(document.body.scrollHeight,document.body.offsetHeight);
            var viewportHeight = window.innerHeight || 
                document.documentElement.clientHeight ||
                document.body.clientHeight || 0;
            var scrollHeight = window.pageYOffset ||
                document.documentElement.scrollTop ||
                document.body.scrollTop || 0;
            // console.log(document.body.scrollHeight);
            // console.log(document.body.offsetHeight);
            // console.log(pageHeight);
            // console.log(viewportHeight);
            // console.log(scrollHeight);

            return pageHeight - viewportHeight - scrollHeight  20;
        }

        function doSomething(){
            var htmlStr = "";
            for(var i=0;i10;i++){
                htmlStr += "这是第"+index+"次加载
";
            }
            $(‘#sample‘).append(htmlStr);
            index++;
            pollScroll();//继续循环
            $(‘#spinner‘).hide();
        }

        function checkScroll(){
            if(!lowEnough()) return pollScroll();

            $(‘#spinner‘).show();
            setTimeout(doSomething,900);

        }
        function pollScroll(){
            setTimeout(checkScroll,1000);
        }
        checkScroll();
    script>
body>
html>