As indicated here (and other places):
This sums it up nicely:
this could make a good addition as an expression for the keyboard plugin? Painless to integrate too with String.fromCharCode(65) == 'A'.
Here is an example from my game where the player is viewing a keycode (which makes no sense) rather than what it says on their keyboard:
<img src="https://dl.dropbox.com/u/1024727/c2/keycode.jpg" border="0">