$("div span")选取里的所有的元素

node2:/var/www/html/js#cat a25.html 
<ul class="test">
<div id=test>aaaa</div>
<div id=test>bbbb</div>
<div id=test><span>cccc</span></div>
</ul >
<ul clas="tlcb">
<p id=scan>eeee</p>
<a id=scan>ffff</a>
<div><span>测试</span></div>
<p id=scan>gggg</p>
</ul>
<script type="text/javascript" src="jquery-2.2.2.min.js"></script>    
<script type="text/javascript" src="a25.js"></script>
node2:/var/www/html/js#

node2:/var/www/html/js#cat a25.js
$("div span").css("background","#bbffaa");