$("div span")选取里的所有的元素

选择器                         描述                                              返回                     示例 

$("ancestor  descendant")      选取ancestor元素了的所有descendant(后代)元素     集合元素  


$("div span")选取<div>里的所有的<span>元素 

node2:/var/www/html/jquery#cat t19.html 
<span>aaaaaaaaaaaaaa</span>
<span>bbbbbbbbbbbbbb</span>
<span>cccccccccccccc</span>
<div>dddddddddddddd</div>
<div>eeeeeeeeeeeeee</div>
<div><span>fffffffff</span></div>
<div><span>ggggggggg</span></div>
<div>hhhhhhhhhhhhhh</div>
<script type="text/javascript" src="jquery-2.2.2.min.js"></script>
<script type="text/javascript" src="t19.js"></script>


node2:/var/www/html/jquery#cat t19.js
$("div span").css("background","red");