JavaScript实现导航栏吸顶效果详解

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title></title>
 <style>
 *{margin: 0;padding: 0;list-style: none;border:none}
 img{vertical-align: top;width: 100%;}
 section{width: 70%;margin: 0 auto;}
 .nav{position: fixed;left: 0;top: 0;width: 100%}
 </style>
</head>
<body>
 <header id="head">
 <img src="images/top.png" alt="">
 </header>
 <nav id="nav">
 <img src="images/nav.png" alt="">
 </nav>
 <section>
 <img src="images/body01.png" alt="">
 <img src="images/body02.png" alt="">
 </section>
 <script src="../../MyTools/MyTools.js"></script>
 <script>
 window.addEventListener('load',function (ev) {
  // 1. 求出头部高度
  var navTopHeight = myTool.$('nav').offsetTop;
  // 2. 监听页面滚动
  window.addEventListener('scroll',function (ev1) {
  var scrollTopHeight = myTool.scroll().top;
  // 2.1 判断
  if(scrollTopHeight >= navTopHeight){
   myTool.addClassName(myTool.$('nav'),'nav')
  }else{
   myTool.removeClassName(myTool.$('nav'),'nav');
  }
  })
 })
 </script>
</body>
</html>