Matching multiple optional characters depending on each other

Question

I want to match all valid prefixes of substitute followed by other characters, so that

• sub/abc/def matches the sub part.
• substitute/abc/def matches the substitute part.
• subt/abc/def either doesn't match or only matches the sub part, not the t .

My current Regex is /^s(u(b(s(t(i(t(u(te?)?)?)?)?)?)?)?)?/ , which works, however this seems a bit verbose.

Is there any better (as in, less verbose) way to do this?

Answer 1

This would do like the same as you mentioned in your question.

^s(?:ubstitute|ubstitut|ubstitu|ubstit|ubsti|ubst|ubs|ub|u)?

The above regex will always try to match the large possible word. So at first it checks for substitute , if it finds any then it will do matching else it jumps to next pattern ie, substitut , likewise it goes on upto u .

DEMO 1 DEMO 2

Answer 2

you could use a two-step regex

1. find first word of subject by using this simple pattern ^(\\w+)
2. use the extracted word from step 1 as your regex pattern eg ^subs against the word substitute