I have a List which looks like the following: http://jsfiddle.net/UwPTF/

<ul class="uol">
      <li>beta</li>
      <li>gamma</li>
      <li>alpha</li>
    <li>beta</li>
    <li>zeta</li>
    <li>BETA</li>            
</ul>

I have 2 buttons, one to highlight the items that are duplicate and the other to remove the duplicate items.

I am trying to use the filter function. If you can explain your code, it's highly appreciated.