title: What is the value of a select when a disabled option is selected?
body: <p>I'm using following html to get the selected-by-default disabled option "Select a town" as a kind of placeholder.  </p>
  
  <pre><code>&lt;select name="town"&gt;
      &lt;option selected disabled value="xx"&gt;-- Select a town --&lt;/option&gt;
      &lt;option value="1"&gt;Paris&lt;/option&gt;
      &lt;option value="2"&gt;London&lt;/option&gt;
      &lt;option value="3"&gt;Budapest&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>Now I'd like to test if any option has been selected by the user, or if it's still empty.<br>
  I thought testing the select value using jquery ( <code>$('select[name="town"]').val();</code> ) would return the value "xx".<br>
  Instead of that, <code>.val()</code> returns null.</p>
  
  <p>I found no trace of this behaviour in the doc (<a href="http://api.jquery.com/val/" rel="nofollow noreferrer">http://api.jquery.com/val/</a>).</p>
  
  <p>Can I rely on <code>.val()</code> returning null when a disabled option is selected? Is it documented anywhere?</p>
  
  <p>Or do I have to check against both null and the actual value of the <code>value</code> attribute ("xx" in the above example)?</p>