<!doctype html>
<html>
<style>
body{
margin:0;
padding:0;
}
#top{
background:#000;
width:400px;
height:30px;
}
.a{
position:fixed;
top:0;
left:0;
}
</style>
<body>
<div style="height:300px;width:100%;background:#ccc;">
</div>
<div id="top">
</div>
<div style="height:1900px;">
</div>
<script>
window.onscroll=function(){
var t = document.documentElement.scrollTop || document.body.scrollTop;
var Otop = document.getElementById(‘top‘);
if(t > 300){
var A = Otop.offsetHeight+Otop.offsetTop;
Otop.style.position=‘fixed‘;
Otop.style.left=‘0‘;
Otop.style.top=‘0‘;
}else{
Otop.style.position=‘‘;
}
}
</script>
</body>
</html>
时间： 2024-10-13 07:26:47