regex for comma-delimited list of two possible valid strings

Question

I'm looking to create a regex that would match either xxx or yyy, or any combination separated by commas.

So these would be valid:

xxx
yyy
xxx,xxx
yyy,xxx
xxx,yyy,yyy,yyy

But these would be invalid:

xx // must be exact xxx
yyyy // must be exact yyy
xxx, // trailing comma
xxxyyy // no delimiter
xxx,,yyy // should only have one comma between
,xxx,yyy // no prepending commas

What have you tried? What didn't work? What did you get? What did you expect? What doesn't work with your code and where is it? — Toto, Feb 22 '20 at 19:56

Eraklon · Accepted Answer · 2020-02-22T18:47:00.657

1

This should suffice ^((?:xxx|yyy)(,(?:xxx|yyy))*)$. https://regex101.com/r/gT8wK5/1327

edited Feb 22 '20 at 18:47

answered Feb 22 '20 at 18:38

Eraklon

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Updated it, it matched the `xxxyyy` case before, sry. – Eraklon Feb 22 '20 at 18:48

score 1 · Answer 2 · answered Feb 22 '20 at 19:33

1

You can use negative lookahead like this:

^((xxx|yyy)(,(?!$)|$))+$

See it on regex101.

Compared to Eraklon's answer this regex doesn't repeat (xxx|yyy) part twice, but it's a little less performant.

answered Feb 22 '20 at 19:33

TeWu

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regex for comma-delimited list of two possible valid strings

2 Answers2