Disabling a submit button using JQuery if a value has not been selected from a specific dropdown
<p>I am trying to disable a submit button if a value from a specific dropdown has not been selected.  The code for the dropdown and button looks like this:</p>

<pre><code>    &lt;li&gt;
    &lt;select name="names" id="names"&gt;
    &lt;option value=""&gt;Constituency&lt;/option&gt;
    &lt;!-- populates the drop down with names --&gt;
    &lt;?php foreach ($cons as $constituency): ?&gt;
    &lt;option value="&lt;?php htmlout($constituency['ids']); ?&gt;"&gt;
    &lt;?php htmlout($constituency['names']); ?&gt;
    &lt;/option&gt;
    &lt;?php endforeach; ?&gt;
    &lt;?php if (isset($selectError)): ?&gt;
    &lt;p&gt;&lt;?php htmlout($selectError); ?&gt;&lt;/p&gt;
    &lt;?php endif; ?&gt;
    &lt;/select&gt;
    &lt;/li&gt;

    &lt;li&gt;&lt;input type="hidden" name="action" value="search"&gt;&lt;/li&gt;
    &lt;li&gt;&lt;input type="submit" value="SEARCH" class="button search" id="jsbutton" disabled="disabled"&gt;&lt;/li&gt;
</code></pre>

<p>So the dropdown has an id of 'names' and the button has an id of 'jsbutton' and is set to 'disabled' .</p>

<p>I then try to target it with the following JQuery but the button remains disabled regardless:</p>

<pre><code>    $(document).ready(function() {

    if ($('#names').val() = '')
    {
        $('#jsbutton').attr('disabled', 'disabled');  
    }
    else
    {
        $('#jsbutton').removeAttr('disabled');
    }
    });
</code></pre>

<p>So what I am trying to do is:</p>

<ul>
<li>Check if value has been selected from dropdpwn.</li>
<li>IF it hasn't then leave button disabled.</li>
<li>ELSE a value has been selected from the dropdown and therefore the button should be enabled.</li>
</ul>

<p>Any help on this is appreciated.</p>

<p>PHP TO POPULATE THE DROPDOWN:</p>

<pre><code>          try
      {
        $cons_result = $pdo-&gt;query("SELECT id, name 
                               FROM constituency 
                               ORDER BY name");
      }
      catch (PDOException $e)
      {
        $error = 'Error fetching constituencies from database!' . $e-&gt;getMessage();
        include 'error.html.php';
        exit();
      }


      foreach ($cons_result as $rows)
      {
        $cons[] = array('ids' =&gt; $rows['id'], 'names' =&gt; $rows['name']);
      }

      include 'searchform.html.php';
    }
</code></pre>
