通过jQuery插件Theia Sticky Sidebar，可以实现智能侧边栏跟随固定范围浮动的效果。本文讲的是不用“theia-sticky-sidebar”也能实现侧栏跟随效果，不过根据我的使用发现有点小bug，自己根据需要自行选择吧。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script src="https://code.jquery.com/jquery.min.js"></script>
<script>
$(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');
}
});
});
</script>
<style>
body {
margin: 10px auto;
font-family: sans-serif;
width: 500px;
}
div {
border-radius: 5px;
box-shadow: 1px 2px 5px rgba(0,0,0,0.3);
border: 1px solid #ccc;
padding: 5px;
}
#sidebarWrap {
height: 1400px;
width: 210px;
float: right;
position: relative;
box-shadow: none;
border: none;
margin: 0;
padding: 0;
}
#main {
width: 270px;
height: 4000px;
}
#footer {
clear: both;
margin: 10px 0;
}
#sidebar {
width: 200px;
height: 1300px;
position: absolute;
background: #ff0;
}
.bar1{height:300px;background: #f00;}
.bar2{background: #0f0;height: 300px;}
.bar3{background: #00f;height: 300px;}
#header {
height: 200px;
margin-bottom: 10px;
}
#sidebar.fixed {
position: fixed;
top: 0;
}
#footer { height: 600px; }</style>
<title>侧栏跟随</title>
</head>
<body>
<div id="header">header</div>
<div id="sidebarWrap">
<div id="sidebar"><div class="bar1">Sidebar</div><div class="bar2"></div><div class="bar3"></div></div>
</div>
<div id="main">Main</div>
<div id="footer">footer</div>
</body>
</html>
