Practice/simplelazyload.html at master · zuolg/Practice · GitHub

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<!DOCTYPE HTML>

<style>
     .A, .B {
          border: 1px solid #CCC;
          background: #EFEFEF;
          margin-bottom: 60px;
          line-height: 300px;
          text-align: center;
          font-size: 40px;
     }
     .A {
          height: 1000px;
     }
     .B {
          background: yellow;
          height: 300px;
     }
</style>

<div id="wrap">
     <div class="A">撑高用的</div>
     <div class="B">懒加载</div>
     <div class="B">懒加载</div>
     <div class="B">懒加载</div>
     <div class="B">懒加载</div>
     <div class="B">懒加载</div>
</div>

<script src="http://code.jquery.com/jquery-1.8.2.js"></script>
<script>
     var $lazyModules = $(".B");
     $(window).on("scroll", function(){
          var sTop = $(this).scrollTop();
          var wH = $(this).height();
          $lazyModules.each(function(index, item){
               var $item = $(item);
               if(!$item.hasClass("loaded") && ($item.offset().top) < wH + sTop){
                    $item.addClass("loaded").hide().fadeIn(1000);
               }
          });
          if($(".loaded").length == $lazyModules.length){
               $(window).off("scroll");
          }
     }).trigger("scroll");
</script>