Question

Regular expression only for checking only if the string is valid, not for capturing any part of it:

ISO 639-1 two-letter lowercase culture code and an ISO 3166-1 two-letter uppercase subculture code, or a ISO 639-1 lowercase culture code by itself.

That is it, it-IT for example. I ended up (I’m not so good in regular expression) with this:

^[a-z]{2}(-[A-Z]{2})?$

Using the capturing group (the 3166-1 part). Is the group really needed? How can avoid using it?

Answer 1

You need to use

^[a-z]{2}(?:-[A-Z]{2})?$

To define non-capturing group you use (?:)