Conditional regex javascript

Question

I'm trying to make a regex which can match a phone number and so tell me if the phone number is either valid or not.

I would like to verify if there is a country id before the phone number, this one is well formated.

For example : +(33)0123456789 I want to be sure if the user start to type the first parenthesis it must be followed by number and ended by a closing parenthesis.

I have succeeded with PCRE engine

^[+]?((\()?(?(2)[0-9]{1,4})(?(2)\)))?([0-9]{2}){1}([\.\- ]?[0-9]{2}){4}$

But I realized this way doesn't work with javascript engine, conditional is not supported.

^[+]?((\()?((?=\2)[0-9]{1,4})((?=\2)\)))?([0-9]{2}){1}([\.\- ]?[0-9]{2}){4}$

It doesn't fill my needs. I want to check if the first parenthesis is set then it must be followed by number and a closing parenthesis.

So I ask you if there is a workaround in javascript to do this ?

Some help would be really appreciated, thank you :)

It sounds as if you just want to make (\d{1,4}) optional. Try ^\+?((?:$[0-9]{1,4})$)?([0-9]{2})([. -]?[0-9]{2}){4}$, see this demo. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 12, 2018 at 13:49
Exactly what I want to do ! It seems that conditional regex is not what I need for this case. I stubbornly tried to use it but your workaround is much more simplen thank you — Hurobaki
– Hurobaki, Commented Dec 12, 2018 at 13:53

Wiktor Stribiżew · Accepted Answer · 2018-12-12 13:56:38Z

1

The (($)?(?(2)[0-9]{1,4})(?(2)$))? part of the regex is matching an optional sequence of smaller patterns. ($)? matches an optional ( and places it in Group 2. Then, (?(2)[0-9]{1,4}) matches 1 to 4 digits if Group 2 matched. Then (?(2)$) matches ) if Group 2 matched. Basically, this is equal to (?:$[0-9]{1,4})$)?.

Thus, you need no conditional construct here.

You may use

^\+?(?:\([0-9]{1,4})\)?[0-9]{2}(?:[. -]?[0-9]{2}){4}$

See the regex demo

Details

^ - start of string
\+? - an optional +
(?:$[0-9]{1,4})$? - an optional sequence: (, 1 to 4 digits and )
[0-9]{2} - 2 digits
(?:[. -]?[0-9]{2}){4} - 4 occurrences of an optional space, dot or - followed with 2 digits
$ - end of string.

answered Dec 12, 2018 at 13:56

Wiktor Stribiżew

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