<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			*{padding: 0;margin: 0;}
			ul{
				list-style: none;
			}
			ul li{
				width: 100px;
				height: 40px;
				line-height: 40px;
				text-align: center;
				background: #87CEEB;
				float: left;
			}
			ul li.active{
				background: #00FF00;
			}
		</style>
		<script src="js/jquery-3.2.1.min.js" type="text/javascript" charset="utf-8"></script>
	</head>
	<body>
		<ul>
			<li>list1</li>
			<li>list2</li>
			<li>list3</li>
			<li>list4</li>
		</ul>
	</body>
	
	<script type="text/javascript">
		
		//用mouseover方法
		$("ul li").mouseover(function(){
			$(this).addClass("active");
		}).mouseout(function(){
			$(this).removeClass("active");
		})
		//结合选择器选择
		$("ul li").mouseover(function(){
			$(this).addClass("active").siblings("li").removeClass("active");
		})
		
	</script>
</html>