<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>导航条案例</title>
<script src="js/jquery-3.3.1.js"></script>
<style type="text/css">
.nav{
width: 400px;
background-color: #FFE4C4;
margin: 0 auto;
position: fixed;
top: 0px;
display: none;
}
.content{
width: 100%;
height: 2000px;
}
</style>
</head>
<body>
<div id="nav" class="nav">搜索框</div>
<div id="head" style="width: 100%; height: 40px; background-color: #A9A9A9"></div>
<div class="content"></div>
</body>
<script type="text/javascript">
var h=$("#head").height()
$(document).scroll(function () {
var scorllTop=$(document).scrollTop();
if(h<scorllTop){
console.log("ok")
$("#nav").css({display:"block"})
}else {
$("#nav").css({display:"none"})
}
})
</script>
</html>
