title: jQuery remove duplicated element
body: <p>What if dom generates duplicated same elements? for example:</p>
  
  <pre><code>    &lt;ul id="listitem"&gt;
       &lt;li&gt;item1&lt;/li&gt;
      &lt;/ul&gt;
  
      &lt;ul id="listitem"&gt;
       &lt;li&gt;item1&lt;/li&gt;
      &lt;/ul&gt;
  
      &lt;ul id="listitem"&gt;
       &lt;li&gt;item1&lt;/li&gt;
      &lt;/ul&gt;
  
  ...
  </code></pre>
  
  <p>Then is this possible to keep one of them and delete extra  two?</p>