title: How to filter select box options with jQuery?
body: <p>I have two select boxes in my form:</p>
  
  <pre><code>&lt;select id="subscription_plan"&gt;
    &lt;option value="basic"&gt;Basic&lt;/option&gt;
    &lt;option value="premium"&gt;Premium&lt;/option&gt;&lt;/select&gt;
  &lt;/select&gt;
  
  &lt;select id="subscription_interval"&gt;
    &lt;option value="basic_monthly"&gt;Monthly&lt;/option&gt;
    &lt;option value="basic_yearly"&gt;Yearly&lt;/option&gt;
    &lt;option value="premium_monthly"&gt;Monthly&lt;/option&gt;
    &lt;option value="premium_yearly"&gt;Yearly&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>How can I filter the options in the second select box based on the option chosen in the first select box?</p>
  
  <p>So, for example, if a user choses the <code>basic</code> option from the first box, only the the two first options of the second box should be displayed.</p>
  
  <p>How can this be done with jQuery?</p>
  
  <p>Thanks for any help and Merry Christmas to all of you.</p>