Question

I want to check if a string matches only some characters with a regex.

For example, I would like to match only a, b, or c.

So, “aaacb” would pass, but “aaauccb” would not (because of the u).

I have tried this way:

/[a|b|c]+/

but it does not work, because the failing example passes.

Answer 1

You need to make sure that your string consists only of those characters by anchoring the regex to the beginning and end of the string:

/^[abc]+$/

You also mixed up two concepts. Alternation (which would be (a|b|c)) and character classes (which would be [abc]). They are in this case equivalent. Your version would also allow | as a character.