html文件：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>突出展示案例</title>
<style type="text/css">
* {
margin: 0;
padding: 0;
}
ul {
list-style: none;
}
body {
background: #000;
}
.wrap {
margin: 100px auto 0;
446px;
height: 394px;
padding:10px 0 0 10px;
background: #000;
overflow: hidden;
border: 1px solid #fff;
}
.wrap li {
float: left;
margin: 0 10px 10px 0;
}
.wrap img {
display: block;
border: 0;
}
</style>
<script src="https://cdn.staticfile.org/jquery/2.0.0/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
//mouseover：鼠标经过事件
//mouseout:鼠标离开事件
//mouseenter:鼠标进入事件
//mouseleave：鼠标离开事件
$(".wrap>ul>li").mouseenter(function(){
$(this).css("opacity","1").siblings().css("opacity","0.4");
});
$(".wrap").mouseleave(function(){
//让所有的li都变亮
//$("li");
//$(".wrap li");
//$(".wrap>ul>li")
//$(this).children().children("li");
$(this).find('li').css("opacity", 1);
})
})
</script>
</head>
<body>
<div class="wrap">
<ul>
<li><a href="#"><img src="https://images.cnblogs.com/cnblogs_com/luwn/1701485/t_200415035849d3a83afb3f3b8c1bb4ac77a2e61a5eae.jpg" alt=""></a></li>
<li><a href="#"><img src="https://images.cnblogs.com/cnblogs_com/luwn/1701485/t_200415035849d3a83afb3f3b8c1bb4ac77a2e61a5eae.jpg" alt=""></a></li>
<li><a href="#"><img src="https://images.cnblogs.com/cnblogs_com/luwn/1701485/t_200415035849d3a83afb3f3b8c1bb4ac77a2e61a5eae.jpg" alt=""></a></li>
<li><a href="#"><img src="https://images.cnblogs.com/cnblogs_com/luwn/1701485/t_200415035849d3a83afb3f3b8c1bb4ac77a2e61a5eae.jpg" alt=""></a></li>
<li><a href="#"><img src="https://images.cnblogs.com/cnblogs_com/luwn/1701485/t_200415035849d3a83afb3f3b8c1bb4ac77a2e61a5eae.jpg" alt=""></a></li>
<li><a href="#"><img src="https://images.cnblogs.com/cnblogs_com/luwn/1701485/t_200415035849d3a83afb3f3b8c1bb4ac77a2e61a5eae.jpg" alt=""></a></li>
</ul>
</div>
</body>
</html>