switch (oEvent.keyCode) {
       case 38: //up arrow  
       case 40: //down arrow
       case 37: //left arrow
       case 39: //right arrow
       case 33: //page up  
       case 34: //page down  
       case 36: //home  
       case 35: //end                  
       case 13: //enter  
       case 9: //tab  
       case 27: //esc  
       case 16: //shift  
       case 17: //ctrl  
       case 18: //alt  
       case 20: //caps lock
       case 8: //backspace  
       case 46: //delete
           return true;
           break;

       default: 

Note: When capturing combination keys there is dedicated boolean attributes for each of the special keys (CTRL, SHIFT, ALT).
Reference: Make Life Easy With Autocomplete Textboxes [JavaScript & AJAX Tutorials] [sitepoint.com]

Press any key to determine the javascript key code of that key. This is a simple script:

<script language="JavaScript">
document.onkeydown = checkKeycode
function checkKeycode(e) {
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
alert("keycode: " + keycode);
}
</script>

You may also use this sort of function to disable certain keys, by adding a void(0) in the function as shown. This essentially tells the page to cancel the last event, e.g. the pressing of that certain key. In the example below, the key that is disabled is the enter key.

<script language="JavaScript">
document.onkeydown = checkKeycode
function checkKeycode(e) {
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
if(keycode == 13){
void(0);
}
}
</script>

This text was copied verbatim from the'Javascript keyCode checker tool' page http://www.ryancooper.com/resources/keycode.asp

This extract of JavaScript code illustrates how the value of a text box on an HTML form could be saved efficiently when used with AJAX.

<input type="text" name="proj1" id="proj1" value="Car_log" 
  onkeyup="timed_updateSummaryCRecord(event.keyCode, '1','project', this.value)" />

The onkeyup event retrieves the user input as soon as the key is pressed, then the event.keyCode is validated to ensure only alpha-numeric characters trigger the save routine.

function timed_updateSummaryCRecord(keyCode, parent_id, field,  val) {
  if (val.length > 0 && ((keyCode > 40) || (keyCode == 8)) ) {
    clearTimeout(t);
    t = setTimeout("updateSummaryCRecord('" + parent_id + "', '" + field + "', '" + val + "')", 1000);
  }
}

The setTimeout will trigger the save routine after 1 second, however if the user continues to type before the 1 second timer has elapsed, the running timer will be cancelled and the new timer will start.

Note: keyCode value '8' is accepted because it is the backspace key. It would also be helpful to accept the delete key press.