Regex define two lists of allowed characters/digits

Question

I'm working on a phone number regex and this is what I have so far: ^[0-9~+ ]{8,20}$

It allows digits between 0 and 9, and '+' and whitespace are allowed as well. The range has to be somewhere between 8 and 20. This works fine.

What I want further is to have 8 to 20 of digits only, where '+' and whitespace come separate from them.

Something like this: ^[+ ]\\d{8,20}$

Suggestions?

Answer 1

How about:

^(?:[+ ]*\d){8,20}$

This will match from 8 to 20 digits preceded or not by + or space.

If the + can be only at the beginig:

^[+]?(?:[ ]*\d){8,20}$