功能：
滚动页面时div到达顶部时固定在顶部
原生实现：
<!DOCTYPE html>
<html>
<head>
<title></title>
<style type="text/css">
#title{
background: #ddd;
width: 100%;
padding:30px;
box-sizing: border-box;
}
</style>
</head>
<body>
<div class="a" style="height:200px;"></div>
<div id="title">hello world</div>
<div class="d" style="height: 1000px;"></div>
<script>
var a;
var title = document.getElementById('title');
var v = title.offsetTop;//存储原来的距离顶部的距离
window.onscroll = function(){
a = document.documentElement.scrollTop;//存储滚动高度
if(a>v){
title.style.position = 'fixed';
title.style.top = 0;
}else if(title.style.position != 'static'){
title.style.position = 'static';
}
}
</script>
</body>
</html>
jquery实现：
<!DOCTYPE html>
<html>
<head>
<title></title>
<style type="text/css">
#text {
background: #ffffff;
width: 100%;
padding:30px;
}
</style>
</head>
<body style="margin:0px;">
<div style="height:300px;background:lightcoral"></div>
<div id="text">div顶部吸附</div>
<div style="height:2000px;background:lightblue"></div>
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
<script type="text/javascript">
$(function() {
var ie6 = document.all;
var dv = $('#text');
var st;
dv.attr('otop', dv.offset().top); //存储原来的距离顶部的距离
$(window).scroll(function() {
st = Math.max(document.body.scrollTop || document.documentElement.scrollTop);
if (st > parseInt(dv.attr('otop'))) {
if (ie6) { //IE6不支持fixed属性，所以只能靠设置position为absolute和top实现此效果
dv.css({ position: 'absolute', top: st });
} else if (dv.css('position') != 'fixed'){
dv.css({ 'position': 'fixed', top: 0 });
}
} else if (dv.css('position') != 'static') {
dv.css({ 'position': 'static' });
}
});
});
</script>
</body>
</html>
