jQuery remove nested ul/li
<p>How do I use jQuery to delete all the elements under "li_1" (but not delete li_1)</p>

<pre><code>&lt;ul id="ul_1"&gt;
   &lt;li id="li_1"&gt;1.1    //want to delete all its child elements
      &lt;ul id="ul_1.1"&gt;    
          &lt;li id="li_1.1.1"&gt;1.1.1&lt;/li&gt;
          &lt;li id="li_1.1.2"&gt;1.1.2
              &lt;ul id="ul_1.1.2"&gt;
                 &lt;li id="li_1.1.2.1"&gt;1.1.2.1&lt;/li&gt;
                 &lt;li id="li_1.1.2.2"&gt;1.1.2.2&lt;/li&gt;
              &lt;/ul&gt;
          &lt;/li&gt; 
      &lt;/ul&gt;
   &lt;/li&gt;
   &lt;li id="li_2"&gt;1.2&lt;/li&gt;
   &lt;li id="li_3"&gt;1.3&lt;/li&gt;
&lt;/ul&gt;
</code></pre>
