title: jQuery check only enabled checkboxes
body: <p>My checkboxes:</p>
  
  <pre><code>&lt;input disabled="disabled" class="Spec" type="checkbox" value="1" /&gt;
  &lt;input class="Spec" type="checkbox" value="2" /&gt;
  &lt;input disabled="disabled" class="Spec" type="checkbox" value="5" /&gt; 
  &lt;input class="Spec" type="checkbox" value="8" /&gt; 
  &lt;input disabled="disabled" class="Spec" type="checkbox" value="10" /&gt;  
  &lt;input class="Spec" type="checkbox" value="30" /&gt;
  </code></pre>
  
  <p>My jQuery selects all the checkboxes regardless of whether they are enabled or disabled - is it possible to only check those that are enabled?</p>
  
  <pre><code>$('#Spec_all').on('click', function() {
      $('.Spec').attr('checked', $(this).is(":checked"));
  });
  </code></pre>