How to make some parts of a regex pattern conditional?

Question

I checked this forum for a answer to my problem, but couldnt find. Experts please help.

I have a problem to validate a string say first name. I am given a set of rules which the string needs to honor and the same needs to be confirmed with regex. I wrote a pattern. Except one rule my pattern honors everything else. I am listing my regex pattern below

([A-Za-z]+[-'!` ]?)*

I am checking for a string say first or last name which needs to start with a alphabet and can have any one of (- or ! or ' or ` or spaces ) these 5 characters ONE AND ONLY IF there is a second word. If a name has 2 words with a space in between then its ok. some examples

List of Valid Names
TIMOTHY
JONATHON
PATRICK
B`ELLA
SUZY JANE - Only one space allowed
SUZY-JANE

List of Invalid Ones
T~ELLA - Because this ~ is not part of regex
SUZY - JANE - No space allowed between hyphens
SUZY  JANE - 2 spaces betweeb words not allowed
GRACO&LAME - & is not allowed

My regex passes all these above conditions But fails when the name ends in any one of the special character. For example, if I give JOHN- OR JOHN' OR JOHN! OR JOHN` OR JOHN (with s spaces at the end) these are not valid but my regex isnt able to handle it

Can some one tell me how to write a conditional regex? Like one and only if there is a second word then the regex pattern must allow the entry of these special characters.

Answer 1

Try this

[A-Za-z]+(?:[-'!` ]?[A-Za-z]+)?

You can check it online here: regexr

The second part

(?:[-'!` ]?[A-Za-z]+)? 

is a non capturing group, this group is because of the ? at the end optional.

Answer 2

Let Name be the regex for the simple name, Special the set of special characters (including the space). Then your final regex looks like

Name(SpecialName)?