Right, I don't mean to confuse anyone BUT...
"a".charCodeAt(0) returns 97
"a".charCodeAt(0)-96 returns 1
that's the encryption problem solved...

charCodeAt is the quickest way to retrieve the character code AND can also be used for validation:
if(char.charCodeAt(0)>=65 && char.charCodeAt(0)<=122){
// do the thing
}
there's no need for long string constants OR regular expressions.

then all you need is to build a decent interface, which you guys seems to be doing.



This might be usefull:
www.lookuptables.com - ASCII Table