title: Enable / Disable dropdown list based on another dropdown list
body: <p>I have two dropdown lists.</p>
  <pre><code>    &lt;select id=&quot;cat_user&quot;&gt;             
       &lt;option value=&quot;Super Admin&quot;&gt;Super Admin&lt;/option&gt;
       &lt;option value=&quot;Event Admin&quot;&gt;Event Admin&lt;/option&gt;
      &lt;/select&gt;
  </code></pre>
  <pre><code>    &lt;select id=&quot;event_name&quot;&gt;             
       &lt;option value=&quot;ICT&quot;&gt;ICT&lt;/option&gt;
       &lt;option value=&quot;Fun Run&quot;&gt;Fun Run&lt;/option&gt;
      &lt;/select&gt;
  </code></pre>
  <p>I want that the second drop-down list should get enabled only if we choose <code>Event Admin</code> in the first drop-down list. It should again get disabled if we deselect the <code>Event Admin</code> from the first drop-down list.</p>
  <blockquote>
  <p>May I know how can this be achieved using javascript?</p>
  </blockquote>