title: Show/Hide element in dropdown depending another dropdown
body: <p>I have 2 dropdown :</p>
  
  <pre><code>&lt;select id="MainList"&gt;
      &lt;option value="0"&gt;----&lt;/option&gt;
      &lt;option value="1"&gt;A&lt;/option&gt;
      &lt;option value="2"&gt;B&lt;/option&gt;
      &lt;option value="3"&gt;C&lt;/option&gt;
      &lt;option value="4"&gt;D&lt;/option&gt;
  &lt;/select&gt;
  
  &lt;select id="ChildList"&gt;
      &lt;option value="0"&gt;----&lt;/option&gt;
      &lt;option value="5"&gt;E&lt;/option&gt;
      &lt;option value="6"&gt;F&lt;/option&gt;
      &lt;option value="7"&gt;G&lt;/option&gt;
      &lt;option value="8"&gt;H&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>I'd like when I select the value "B" in the first dropdown hide or disable some values in the ChildList. Sample if : C in first hide or disable G in second, if D in first hide or disable G and H in second.</p>
  
  <p>Thanks</p>