Regex capture required and optional characters in any position only

Question

I would like to match against a word only a set of characters in any order but one of those letters is required.

Example:

• Optional letters: yujkfec
• Required letter: d

Matches: duck dey feed yudekk dude jude dedededy jejeyyyjd
No matches (do not contain required): yuck feck
No matches (contain letters outside of set): sucked shock blah food bard

I've tried ^[d]+[yujkfec]*$ but this only matches when the required letter is in the front. I've tried positive lookaheads but this didn't do much.

Answer 1

You can use

\b[yujkfec]*d[dyujkfec]*\b

See the regex demo . Note that the d is included into the second character class.

Details :

• \b - word boundary
• [yujkfec]* - zero or more occurrences of y , u , j , k , f , e or c
• d - a d char
• [dyujkfec]* - zero or more occurrences of y , u , j , k , f , e , c or d .
• \b - a word boundary.