Validating a string.

[Adam David Moss]

Hello,

I have a requirement whereby I must validate that a string matches one of
several patterns:

1. An ISO standard 2 character country code (eg GB, NL) followed by five
digits.
2. An ISO standard 2 character country code (eg GB, NL) followed by an X
followed by five digits.
3. 3 characters in the range a-z followed by 3 digits followed by 2
characters in a specific set (eg MT, AT, DA).
4. 4 characters followed by a hash (#) followed by 3 characters followed by
3 digits followed by a hash followed by 3 characters.
5. 4 characters followed by a hash (#) followed by 3 characters followed by
3 digits followed by a hash followed by 4 characters.

I have been told that a better way to achieve this than using .charAt is by
using something called a regular expression, but I don't really understand
them. Can anyone please advise on the above or alternatively point me in
the direction of a suitable resource on these regular expression things?

Cheers,


Adam M.

[Bill Chalmers]

Re: Validating a string.

This one is quite good:

http://www.javascriptkit.com/javatutors/re.shtml

"Adam David Moss" <admoss@nospamg lobalnet.co.uk> wrote in message
news:bfegcp$f67 $2@sparta.btint ernet.com...[color=blue]
> Hello,
>
> I have a requirement whereby I must validate that a string matches one of
> several patterns:
>
> 1. An ISO standard 2 character country code (eg GB, NL) followed by five
> digits.
> 2. An ISO standard 2 character country code (eg GB, NL) followed by an X
> followed by five digits.
> 3. 3 characters in the range a-z followed by 3 digits followed by 2
> characters in a specific set (eg MT, AT, DA).
> 4. 4 characters followed by a hash (#) followed by 3 characters followed[/color]
by[color=blue]
> 3 digits followed by a hash followed by 3 characters.
> 5. 4 characters followed by a hash (#) followed by 3 characters followed[/color]
by[color=blue]
> 3 digits followed by a hash followed by 4 characters.
>
> I have been told that a better way to achieve this than using .charAt is[/color]
by[color=blue]
> using something called a regular expression, but I don't really understand
> them. Can anyone please advise on the above or alternatively point me in
> the direction of a suitable resource on these regular expression things?
>
> Cheers,
>
>
> Adam M.
>
>[/color]

[Dr John Stockton]

Re: Validating a string.

JRS: In article <bfegcp$f67$2@s parta.btinterne t.com>, seen in
news:comp.lang. javascript, Adam David Moss
<admoss@nospamg lobalnet.co.uk> posted at Sun, 20 Jul 2003 16:35:38 :-[color=blue]
>Hello,
>
>I have a requirement whereby I must validate that a string matches one of
>several patterns:
>
>1. An ISO standard 2 character country code (eg GB, NL) followed by five
>digits.
>2. An ISO standard 2 character country code (eg GB, NL) followed by an X
>followed by five digits.
>3. 3 characters in the range a-z followed by 3 digits followed by 2
>characters in a specific set (eg MT, AT, DA).
>4. 4 characters followed by a hash (#) followed by 3 characters followed by
>3 digits followed by a hash followed by 3 characters.
>5. 4 characters followed by a hash (#) followed by 3 characters followed by
>3 digits followed by a hash followed by 4 characters.
>
>I have been told that a better way to achieve this than using .charAt is by
>using something called a regular expression,[/color]

Agreed.
[color=blue]
> but I don't really understand
>them. Can anyone please advise on the above[/color]

Some may construct a single vast RegExp to do it. I would merge 12 & 45
only. Ignoring that some 2-letter patterns are not at present
countries, to get started,

function TryIt(S) {
if (/^([A-Z]{2})X?\d{5}$/.test(S)) return 12
if (/^([a-z]{3})\d{3}([A-Z]{2})$/.test(S)) return 3
if (/^....#...\d{3}# ....?$/.test(S)) return 45
return 0 } // lightly tested

The result may be used as, or cast to, a boolean; or used to show which
rule fired.

In the first two cases, RegExp.$1 (& RegExp.$2) contained matched
fields, which can be tested against a list of valid ones :

OK = "UK NL RU MX ...".indexOf(Re gExp.$1+" ") != -1 // lightly tested
[color=blue]
> or alternatively point me in
>the direction of a suitable resource on these regular expression things?[/color]

Dillons, Waterstones, maybe Foyles, etc.; any good Public, College, or
University Library.

Before going, read <URL:http://www.merlyn.demo n.co.uk/js-other.htm#RE>,
to get a slight general idea.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
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