title: Get checkbox attribute with jQuery
body: <p>For example I have several checkboxes.</p>
  
  <pre><code>&lt;input type="checkbox" value="27" name="option_value[12][]" id="option_value_27"  class="filtered option_value" cat="121"&gt;
  &lt;input type="checkbox" value="27" name="option_value[12][]" id="option_value_27"  class="filtered option_value" cat="141"&gt;
  </code></pre>
  
  <p>Two questions:</p>
  
  <ol>
  <li>Is the declaration of <code>cat</code> attribute valid?</li>
  <li>How can I get access to <code>cat</code> attribute value for example when I click on button?</li>
  </ol>