title: `String.fromCharCode(keyCode)` doesn't work in Firefox
body: <p><code>String.fromCharCode(keyCode)</code> doesn't work in Firefox. </p>
  
  <p>For example</p>
  
  <ul>
  <li>I press the semicolon key and it throws the 1/4 sign. </li>
  <li>The number pad throws letters. </li>
  </ul>
  
  <p>I am using this to do some field validation, because the <code>event.key</code> attrubute is not supported in FF.</p>