借占位符实现滚动到列表底部重新加载数据

滚动到底部更新数据是个很常见的需求，也是网站优化的一部分。
页面效果
pic1.png
第一次滚动到底部新加载数据
pic2.png
再滚动
pic3.png
源代码
<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>Document</title>
   <style>
       li{width: 100px;height: 100px;background: #000;margin-bottom: 15px;color: #fff;text-align: center;}
   </style>
   <script src="./jquery.min.js"></script>
</head>
<body>
   <ul class="ul-wrap">
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
       <li>1</li>
   </ul>
   <div  id="loadInfo"></div>
   <script>
       function randomColor(){
         var color="#";
         var colorArr=["0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"];
         for(i=0;i<6;i++){
             var cur=randomNum(15,0);
             color+=colorArr[cur];
         }
         function randomNum(max,min){
             return Math.floor(Math.random()*(max-min+1)+min)
         }
         return color;
       }

       //获取滚动高度、文档高度、浏览器视口高度
       var heightFuns=function(){
           //获取滚动高度
           heightFuns.prototype.getScrollTop=function (){
               var scrollTop=0,bodyScrollTop=0,documentScrollTop=0;
               if(document.body){
                   bodyScrollTop=document.body.scrollTop;
               }
               if(document.documentElement){
                   documentScrollTop=document.documentElement.scrollTop;
               }
               scrollTop = (bodyScrollTop-documentScrollTop>0)?bodyScrollTop:documentScrollTop;
               return scrollTop;
           }
           //获取文档的总高度
           heightFuns.prototype.getScrollHeight=function (){
               var scrollHeight=0,bodyScrollHeight=0,documentScrollHeight;
               if(document.body){
                   bodyScrollHeight=document.body.scrollHeight;
               }
               if(document.documentElement){
                   documentScrollHeight=document.documentElement.scrollHeight;
               }
               scrollHeight=(bodyScrollHeight-documentScrollHeight>0)?bodyScrollHeight:documentScrollHeight;
               return scrollHeight;
           }
           //获取浏览器视口的高度
           heightFuns.prototype.getWindowHeight=function (){
               var windowHeight=0;
               if(document.compatMode == 'CSS1Compat'){
                   windowHeight=document.documentElement.clientHeight;
               }else{
                   windowHeight=document.body.clientHeight;
               }
               return windowHeight;
           }
       }

       function showData(){
           $(".ul-wrap").append("<li>new</li>");
           $("body").css("background",randomColor());
           $("#loadInfo").html("");
       }

       $(function(){
           var heightObj=new heightFuns();
           window.onscroll=function(){
               if(heightObj.getScrollTop()==heightObj.getScrollHeight()-heightObj.getWindowHeight()){
                   // setTimeout(showData,1000);
                   showData();
                   $("#loadInfo").html("正在加载...");
               }
           }
       });
   </script>
</body>
</html>
借占位符实现滚动到列表底部重新加载数据

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