Validating form fields

[Si]

I'm trying to validate VAT Codes entered into a form.

Whats the best way of checking the contents of a form input? For example, Austria's VAT code has the standard template of "U12345678" (a "U" followed by 8 numbers) and I want to check that the first character of the input value is "U"

Has anyone got any ideas?

My current Javascript is:

 var co = document.frmPayment.country.value;
 var vatcode = document.frmPayment.VATCode.value;
 var vatfirst = left(vatcode, 1);
 var vatlen = vatcode.length;
 
 alert("Country = '" + co + "'\nVAT Code = '" + vatcode + "'\nVAT Length = '"+ vatlen + "'\nFirst Character = " + firstchar + "'");
 
 if (co=='040' || co=='056' || co=='620' || co=='208' || co=='246' || co=='442' || co=='250' || co=='276' || co=='300' || co=='372' || co=='380' || co=='528' || co=='724' || co=='752') {
 // if any of the VAT code countries are selected
 
 
  if (vatlen==0) {
   alert("Please enter your VAT code");
   document.frmPayment.VATCode.focus();
   return false;
   
  } else {
   if (co == '040') {  // if the country is austria
	
	if (vatfirst != 'U') {
	 alert ("Please enter a valid VAT code.\n\n Eg. U12345678");
	 document.frmPayment.VATCode.focus();
	 return false;
	} 
   }
  }

 }

BTW, the country selection works fine and the length is detected fine.

Cheers,

[vgarcia]

If everything else works, then this should help you test for a properly formatted VAT code:

var vatcode = document.frmPayment.VATCode.value;
//create regular expression that matches VAT format
var RE = new RegExp('(u|U)[0-9]{8}');
//test regular expression
var myTest = RE.test(vatcode);
If (!myTest) {
//VAT doesn't match format
  alert('Your VAT code does not follow the proper format.');
}
//get out of here.
return myTest;

[Si]

Vinnie mate - you've saved me a long hard afternoon! Never realised JavaScript had a regular expression module built in... even if I had, I wouldn't have know how to use it!!!

Cheers very much!

BTW, have you got any URLs to documentation on how to use the RegExp thing more (eg. all the properties for setting the reg exp?)

Nice one brudda!

[vgarcia]

http://www.webreference.com/js/column5/ for regular expressions in Javascript specifically, and http://www.regexlib.com/CheatSheet.htm is a good "cheat sheet" for Perl-compatible regular expression syntax (Perl-compatible is the type of regexps used in nearly every language, like JS, Java, .NET, PHP, etc.)

[Si]

Sweet - thanks mate!

[vgarcia]

No problem!

[Si]

Actually, I'm going to be a really cheeky bugger and ask for some help on the templates...

What would the following convert to as regexp strings?

(X stands for any alpha character and there are several versions available for some countries)

France
12345678901
X1234567890
1X123456789
XX123456789

(11 characters, alpha either 1st, 2nd, both or neither)

Ireland
1234567X
1X23456X

(8 characters, alpha either 8th character or 2nd and 8th)

Spain
X12345678
12345678X
X1234567X

(9 characters, alpha either 1st, 9th or both characters)



Thanks for any help on this - really could do with getting it fixed this afternoon!

[Si]

No worries - I've sorted it now (multiple regexp instances with "and" conditions).

If anyone else is interested, I'll post the solutions up later (bit busy at the mo).