JavaScript实现图片滚动加载与刷新回顶部的完整方案

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>haorooms前端博客-可视区域加载之 javascript</title>
  <style>
  img{width:100%;margin-bottom: 30px; min-height: 400px; background-color: #ddd;}

  </style>
</head>
<body>
  <img haoroomslazyload="Chrysanthemum.jpg" src="" >
  <img haoroomslazyload="Desert.jpg" src="" >
  <img haoroomslazyload="Hydrangeas.jpg" src="" >
  <img haoroomslazyload="Koala.jpg" src="" >
  <img haoroomslazyload="Lighthouse.jpg" src="" >
  <img haoroomslazyload="Penguins.jpg" src="" >
  <img haoroomslazyload="Tulips.jpg" src="" >
  <script>
  var imgNum=document.getElementsByTagName('img').length;
  var imgObj=document.getElementsByTagName("img");
  var l=0;

    window.onscroll=function(){
        var seeHeight = document.documentElement.clientHeight;
        var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
        for(var i=l;i<imgNum;i++){
          if(imgObj[i].offsetTop < seeHeight + scrollTop){
            console.log(imgObj[i].getAttribute("src"));
            console.log(imgObj[i].src );
            if(imgObj[i].getAttribute("src") == ""){
              imgObj[i].src = imgObj[i].getAttribute("haoroomslazyload");
            }
          }
          if(imgObj[i].offsetTop > seeHeight + scrollTop){
            l=i;
            break;
          }
        }
    }

</script>

var l=0
//js方法翻译版
$(window).bind("scroll", function(event){

        for(var i=l;i<$("img").length;i++){
          if($("img").eq(i).offset().top < parseInt($(window).height()) + parseInt($(window).scrollTop())){
            if($("img").eq(i).attr("src") == ""){
              var lazyloadsrc=$('img').eq(i).attr("haoroomslazyload");
              $("img").eq(i).attr("src",lazyloadsrc);
            }
          }
          if($("img").eq(i).offset().top > parseInt($(window).height()) + parseInt($(window).scrollTop())){
            l=i;
            break;
          }
        }

 });

$(window).bind("scroll", function(event){

     //窗口的高度+看不见的顶部的高度=屏幕低部距离最顶部的高度 
      var thisButtomTop = parseInt($(window).height()) + parseInt($(window).scrollTop()); 
      var thisTop = parseInt($(window).scrollTop()); //屏幕顶部距离最顶部的高度 
        var PictureTop = parseInt($("你的要滚动加载的ID").offset().top); 
         if (PictureTop >= thisTop && PictureTop <= thisButtomTop) {
         // $("#你的要滚动加载的ID").attr("src", $("#你的要滚动加载的ID").attr("haoroomslazyload")); 

          //此处可以执行你的加载函数，加载函数由原来的document.ready中，移到这里来！



         }
})

window.onbeforeunload  =  function(){$(window).scrollTop(0);}