title: how to select only one value per optgroup in multiple selection
body: <p>Hi Im using the  dropdown, i need to select single value per optgroup ,on selection disable other values in that optgroup</p>
  
  <pre><code>    &lt;select style="width:300px"&gt;
      &lt;optgroup label="Alaskan/Hawaiian Time Zone"&gt;
     &lt;option value="AK"&gt;Alaska&lt;/option&gt;
      &lt;option value="HI"&gt;Hawaii&lt;/option&gt;
      &lt;/optgroup&gt;
     &lt;optgroup label="Pacific Time Zone"&gt;
     &lt;option value="CA"&gt;California&lt;/option&gt;
     &lt;option value="NV"&gt;Nevada&lt;/option&gt;
     &lt;option value="OR"&gt;Oregon&lt;/option&gt;
     &lt;option value="WA"&gt;Washington&lt;/option&gt;
     &lt;/optgroup&gt;
     &lt;/select&gt;
  
  
  
  
  $('select').change(function () {
  var opt = $(this).find(':selected');
  var sel = opt.text();
  var og = opt.closest('optgroup').attr('label');
  //alert(sel);
  //alert(og);
       var selects = $('select option').attr('id');
   for (var i=0; i&lt;selects.length; i++) {
      $(selects[i]).find('option').removeAttr('disabled'); 
    }
  </code></pre>
  
  <p>});</p>