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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style>
li{ float:left; width:50px; height:50px; background:red; margin:5px;}
</style>
<script src="jquery-1.11.1.js"></script>
<script>
$(function(){
$("li").click(function(){
//console.log($(this).index());
var $this=$(this).index();
var $length=$('li').length;
for(var i=0;i<$length;i++){
if(i<=$this){
$('li').eq(i).css('background','blue');
}else{
$('li').eq(i).css('background','red');
}
}
})
});
</script>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
<li>4</li>
<li>5</li>
</ul>
</body>
</html>