<html> <head> <title>test</title> </head> <body> <div style="position: fixed; height: 200px; background: red; width: 100%; display: none" id="topbar"></div> <div style="height: 3000px;">content</div> </body> <script type="text/javascript"> window.onscroll = function () { var top = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop; var node = document.getElementById(‘topbar‘); if (top > 500) {//500就是滚动条滚动到的位置，大于500才显示 node.style.display = ‘block‘; } else { node.style.display = ‘none‘; } } </script> </html>
【2017-04-10】js来控制导航栏在滚动条拉到一定位置时显示
原文：http://www.cnblogs.com/qq609113043/p/6690754.html