How do I handle or abort Function Key events (e.g. F1, F2,etc) in both IE and Firefox?

Run this page and you will be shown the keycode for the Function Key you pressed. In addition, any standard browser handlers (such as help prompts when F1 is pressed or Searches when F3 is pressed) will be aborted - so you can pass them to your app instead. See below:

  <script type="text/javascript" language="javascript">
  /////////////////////////////////////////////////////////////////////
  ///Demo Script to display the function key that was pressed
  ///and abort any browser event e.g. F3 for IE find, 
  ///F1 for IE help, F1 for Firefox Help
  /////////////////////////////////////////////////////////////////////
  ///Version      Author          Date            Comment
  ///1.0          DDK             03 Dec 2008     Original Version for 
  ///                                             Application Tender
  ///                                             Proof of concept 
  ///                                             when users wanted 'green
  ///                                             screen' functionality
  /////////////////////////////////////////////////////////////////////
  //debugger;
  document.onkeydown = showDownAndAbortEvent;
  //Stop F1 opening Help in IE
  document.onhelp=function() {return false};
  window.onhelp=function() {return false};
  
  // decipher key down codes
  function showDownAndAbortEvent(evt) 
  {
      //clearCells();
      evt = (evt) ? evt : ((event) ? event : null);
      if (evt) {
          alert('keyCode:' + evt.keyCode + ';charcode' + evt.charCode + ';' )  ;
          try
          {
              evt.preventDefault();  // disable default help in Firefox
              evt.stopPropagation(); 
          }
          catch (ex) {}
          try
          {
              //Kill any intercepts for ie
              window.event.cancelBubble = true;
              window.event.returnValue = false;
              window.event.keyCode = 0;
          }
          catch (ex) {}
          return false;
          }
  }
  </script>