CharAt in a keystroke event using regular expression

Question

I'm working on a canadian postal code field.  I'm using a regular expression to validate the value.
//accepts "A9A 9A9", "A9A9A9" or "" as valid entries excluding letters D, F, I, O, Q, U and W as well as Z as the first digit.
var re = /^[ABCEGHJKLMNPRSTVXY]\d[ABCEGHJKLMNPRSTVWXYZ]( )?\d[ABCEGHJKLMNPRSTVWXYZ]\d$|^$/i;
if(re.test(event.value) == false){
app.alert("Code postal invalide", 0, 0,"CODE POSTAL");
event.value = "";
I also added a keystroke event to prescan every digit and toUpperCase() them.
//accepts letters, numbers, backspace or spaces
var re = /[ABCEGHJKLMNPRSTVWXYZ]|\d|^$|\s/i;
if (!event.willCommit){
if(re.test(event.change) == false){
  event.rc = false;
else{
  event.change = event.change.toUpperCase();
I want to Replicate the behavior of an arbitrary mask where I can force a character to appear at a specific position.  In this example, instead of letting the user decide wether he adds a "space" or not between the two parts of the code, I want to:
1-Remove "\s" in the keystroke regexp so the user cannot use "space";
2-Replace "( )?" for "( )" in the validation regexp;
3-Force a space at charAt(3).
Is it possible to have it appear while the user is still typing or is my only option to change the value once committed or as a cutom format script?
In the same manner, is it possible to specify a different regexp keystroke depending on the position of each character?
charAt(0), charAt(2), charAt(5) would be letters
charAt(1), charAt(6), charAt(7), would be numbers
charAt(3), would automatically add a "space"
in the end, I want the same behavior as an arbitrary mask without the annoying alert when entering a wrong digit.

Answer 1

The entire string validation is different from the keystroke validation. The keystroke validation can check each keystroke as it is typed while the string validation can only process the entire string at one time.
You need to break your RegExp to describe the requirement for each character. You can even specify the possible number of repetitions of the pattern.
A discussion on to create keystroke validations would be far too long for a post in a forum.
Acuumnen has an ebook about Acrobat forms and has a couple of chapters to some simple validation and formatting scripts.