title: Get value of custom attribute
body: <p>I have two radio buttons. I would like to be able to get the value of the custom attribute "xmlvalue" of the checked radio button.</p>
  
  <p>I have tried with the following script:</p>
  
  <pre><code>var userType = $("input[name=ctrl_CustomerType]:checked", this).attr('xmlvalue');
  </code></pre>
  
  <p>Markup:</p>
  
  <pre><code>&lt;input type="radio" name="ctrl_CustomerType" id="ctrl_CustomerType_1" xmltag="CustomerType" xmlvalue="existingCustomer" checked="checked"&gt; Yes
  &lt;br /&gt;
  &lt;input type="radio" name="ctrl_CustomerType" id="ctrl_CustomerType_2" xmltag="CustomerType" xmlvalue="newCustomer"&gt; No
  </code></pre>
  
  <p><a href="http://jsfiddle.net/NrQek/" rel="noreferrer">Fiddle here</a></p>
  
  <p>-- But I keep getting "Undefined".</p>
  
  <p>Any ideas?</p>