图片懒加载--判断div ul中的li是否已经滑动到可视区域里

<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8">

<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=0, minimum-scale=1.0, maximum-scale=1.0">

<title>lazyLoad</title>

<!-- 参考网址  https://segmentfault.com/a/1190000003881643 -->

<style type="text/css" media="all">

 * {

            margin: 0;

            padding: 0;

        }

        #div1 {

            width: 520px;

            margin: 30px auto;

            border: 1px solid red;

            overflow: hidden;

        }

        li {

            width: 160px;

            height: 160px;

            float: left;

            list-style: none;

            margin: 5px;

            background: url(loading.gif) center center no-repeat;

            border: 1px dashed green;

        }

        img{

        width:100%

        }

</style>

</head>

<body>

   <div id="div1">

            <ul>

                <li data-src="http://4493bz.1985t.com/uploads/allimg/140710/1-140G0161612.jpg"></li>

                <li data-src="http://4493bz.1985t.com/uploads/allimg/140628/1-14062Q33R6.jpg"></li>

                <li data-src="http://4493bz.1985t.com/uploads/allimg/140628/1-14062Q33242.jpg"></li>

                <li data-src="http://img.bizhi.sogou.com/images/2014/12/10/997251.jpg"></li>

                <li data-src="http://dl.bizhi.sogou.com/images/2014/12/02/986640.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170473_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170475_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170477_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

                <li data-src="http://imgstore.cdn.sogou.com/app/a/100540002/1170479_s_90_2_219x160.jpg"></li>

            </ul>

        </div>

        <script>

        window.onload = function () {

            window.onscroll();

        };

         window.onscroll = function () {

            var oDiv = document.getElementById('div1');

            var oUl = oDiv.children[0];

            var aLi = oUl.children;

            for (var i = 0, l = aLi.length; i < l; i++) {

                var oLi = aLi[i];

                //检查oLi是否在可视区域

                var t = document.documentElement.clientHeight + (document.documentElement.scrollTop || document.body.scrollTop);

                var h = getH(oLi);

                if (h < t) {

                    setTimeout("setImg(" + i + ")", 500);

                }

                console.log(i);

            }

        };

            function setImg(index){

                var oDiv=document.getElementById("div1")

                var oUl=oDiv.children[0];

                var aLi=oUl.children;

                if (aLi[index].dataset) {

                    var src=aLi[index].dataset.src;

                } else{

                    var src=aLi[index].getAttribute('data-src');

                }

                var oImg=document.createElement('img');

                oImg.src=src;

                if (aLi[index].children.length==0) {

                    aLi[index].appendChild(oImg);

                }

            }

            //获得对象距离页面顶端的距离

            function getH(obj) {

                var h = 0;

                while (obj) {

                    h += obj.offsetTop;

                    obj = obj.offsetParent;

                }

                return h;

            }

        </script>

</body>

</html>
这是整个页面的代码。其中有gitH()函数和判断是否在可视区域。
加油。