js实现吸顶效果 2019年3月19日
前端 
<!doctype html>
<html>
<head>
 <meta charset="utf-8">
 <title>无标题文档</title>
 <style>
  * {
   margin: 0;
   padding: 0;
  }
  #div1 {
   width: 100%;
   height: 50px;
   background: skyblue;
  }
 </style>
 <script>
  window.onload = function() {
   var oDiv = document.getElementById('div1');
   var divT = oDiv.offsetTop;
   //console.log(divT);
   window.onscroll = function() {
    // 获取当前页面的滚动条纵坐标位置 （依次为火狐谷歌、safari、IE678）
    var scrollT = document.documentElement.scrollTop || window.pageYOffset || document.body.scrollTop;
    if (scrollT >= divT) {
     if (window.navigator.userAgent.indexOf('MSIE 6.0') != -1) {
      // 兼容IE6代码
      oDiv.style.position = 'absolute';
      oDiv.style.top = scrollT + 'px';
      oDiv.style.left = 0 + 'px';
     } else { 
      // 正常浏览器代码
      oDiv.style.position = 'fixed';
      oDiv.style.width = '100%';
      oDiv.style.margin= 0;
      oDiv.style.padding=0;
      oDiv.style.zIndex = 999;
      oDiv.style.top = 0;
      oDiv.style.left = 0;
     }
    } else
     oDiv.style.position = '';
   }
  }
 </script>
</head>
<body>
 <div class="all">
  以上<br>
  以上<br>
  以上<br>
  以上<br>
  以上<br>
  以上<br>
  以上<br>
  <div id="div1"></div>
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 </div>
</body>
</html>