title: How to update a select box based on radio button check in Javascript
body: <p>When I click the "Non-technical" radio button I'd like to update the options of 
  select box to "English", "History", "Maths". Both the radio buttons and select box are 
  inside a form. This is my code given below in HTML.</p>
  
  <p>I need a JavaScript validation:</p>
  
  <pre><code>&lt;tr&gt;
      &lt;td&gt;Category:&lt;/td&gt;
      &lt;td&gt;
          &lt;input type="radio" name="category" value="1" checked="yes" /&gt;Technical
          &lt;input type="radio" name="category" value="2" /&gt;Non-technical&lt;/td&gt;
  &lt;/tr&gt;
  &lt;tr&gt;
      &lt;td&gt;Branch&lt;/td&gt;
      &lt;td&gt;
          &lt;select id="techy"&gt;
              &lt;option&gt;Hardware&lt;/option&gt;
              &lt;option&gt;Networking&lt;/option&gt;
              &lt;option&gt;Linux&lt;/option&gt;
      &lt;/td&gt;
  &lt;/tr&gt;
  </code></pre>