需要在页面引用jQuery库.
可以在这里看demo.
HTML代码：
<div id="header">header</div> <div id="sidebarWrap"> <div id="sidebar">Sidebar</div> </div> <div id="main">Main</div> <div id="footer">footer</div>
CSS代码：
body {
margin: 10px auto;
font-family: sans-serif;
500px;
}
div {
border-radius: 5px;
box-shadow: 1px 2px 5px rgba(0,0,0,0.3);
border: 1px solid #ccc;
padding: 5px;
}
#sidebarWrap {
height: 400px;
210px;
float: right;
position: relative;
box-shadow: none;
border: none;
margin: 0;
padding: 0;
}
#main {
270px;
height: 4000px;
}
#footer {
clear: both;
margin: 10px 0;
}
#sidebar {
200px;
height: 300px;
position: absolute;
}
#header {
height: 200px;
margin-bottom: 10px;
}
#sidebar.fixed {
position: fixed;
top: 0;
}
#footer { height: 600px; }
JavaScript代码：
$(function() {
var top = $('#sidebar').offset().top - parseFloat($('#sidebar').css('marginTop').replace(/auto/, 0));
var footTop = $('#footer').offset().top - parseFloat($('#footer').css('marginTop').replace(/auto/, 0));
var maxY = footTop - $('#sidebar').outerHeight();
$(window).scroll(function(evt) {
var y = $(this).scrollTop();
if (y > top) {
if (y < maxY) {
$('#sidebar').addClass('fixed').removeAttr('style');
} else {
$('#sidebar').removeClass('fixed').css({
position: 'absolute',
top: (maxY - top) + 'px'
});
}
} else {
$('#sidebar').removeClass('fixed');
}
});
});