Validation of last 2 characters

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February 22nd, 2012, 02:41 PM

troyjerkins

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JavaScript - Validation of last 2 characters

I have a requirement to validate a 4 character field. The first two characters must be alphanumeric and the last two characters must also be alphanumeric BUT not contain any of these letters: I, O, U or Q.

I rarely ever work with regular expressions but think I am able to come close based on what I have read.

The expression ^([A-Z0-9]{2}\w{2}$) will almost accomplish but does not prevent entering I, O, U or Q in the last 2 characters.

The expression ^([A-Z]{2}[^IiOoUuQq]{2}$) prevents the unwanted charaters but entry of special characters is allowed.

Can anyone help combine these two approaches for the last two characters?

Thanks,

-Troy

February 22nd, 2012, 02:52 PM

Kravvitz

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Welcome to DevShed Forums, Troy.

You can use multiple character ranges within a character class to do validate the last two characters:

Code:

[0-9a-hj-npr-tv-z]{2}

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February 22nd, 2012, 11:08 PM

ragax

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Hi Troy,

In agreement with Kravvitz---he showed you a nice example of multiple ranges of letters in a character class.

Just for the archives, here's another solution that uses a lookahead instead.

Code:

^[A-Z0-9]{2}(?:(?!I|O|U|Q)[A-Z0-9]){2}$

You have to add whatever Javascript needs to make it case-insensitive. I don't program in JS, but according to RB it's something like this:

Code:

boolean foundMatch = subjectString.matches("(?i)^[A-Z0-9]{2}(?:(?!I|O|U|Q)[A-Z0-9]){2}$");

Wishing you both a fun day.

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February 22nd, 2012, 11:53 PM

Kravvitz

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ragax, that might be Java, but it's certainly not JavaScript.

JavaScript doesn't support inline modifiers like that.

Here's how to set modifiers (aka flags) in JavaScript.

February 23rd, 2012, 02:41 AM

ragax

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Kravvitz, you're spot on: I had Java instead of JS in the RB pull-down. You can tell I don't code in Java either! Thank you for pointing out the error and providing a resource about how to set flags in JS regex.

Trying again, here's the JS code that RB generates for the regex I pasted:

Code:

if (/^[A-Z0-9]{2}(?:(?!I|O|U|Q)[A-Z0-9]){2}$/i.test(subject)) {
	// Successful match

Again, that's just for the archives, I see no particular reason to use that in preference to Kravvitz's character class. One approach is "say exactly what you want", the other is "say what you don't want".

Wishing you all a fun day