title: Find duplicates by class and remove
body: <pre><code>&lt;ul class="list"&gt;
      &lt;li class="item_20"&gt;&lt;/li&gt;
      &lt;li class="item_20"&gt;&lt;/li&gt;
      &lt;li class="item_20"&gt;&lt;/li&gt;
      &lt;li class="item_21"&gt;&lt;/li&gt;
      &lt;li class="item_21"&gt;&lt;/li&gt;
      &lt;li class="item_22"&gt;&lt;/li&gt;
      &lt;li class="item_22"&gt;&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>Is there a way with jQuery to determine and remove duplicates BY class in the example above? So only one li remains of every unique class.</p>