jquery中的children()和contents()的区别

 1 <ul id="n1">
 2     test
 3     <li id="n2" class="active">
 4         <span id="n3">菜单1</span>
 5         <ul id="n4">
 6             <li id="n5" class="active">子菜单1-1</li>
 7             <li id="n6">子菜单1-3</li>
 8         </ul>
 9     </li>
10     <li id="n7">
11         <span id="n8">菜单2</span>
12         <ul id="n9">
13             <li id="n10">子菜单2-1</li>
14             <li id="n11" class="active">子菜单2-2</li>
15             <li id="n12">子菜单2-3</li>
16         </ul>
17     </li>
18     <li id="n13"><span id="n14">菜单3</span></li>
19 </ul>