Matching when an arbitrary pattern appears multiple times

问题

I'm trying to write a regex that will succeed when an arbitrary pattern of length 2 or greater appears more than once in a phrase. Essentially, I would like to use a capture group in the search.

Something like this, but generalized to match any phrase, not just foo

/foo.*foo/

For example,

Should match:

abcdabcd     ('abcd' is repeated)
foobarfoo    ('foo' is repeated)
mathematics  ('mat' is repeated)

Should not match:

bar        (no repetition of any pattern)
foo        ('o' is repeated but it is not length>=2)

Can regexes do this? Or should I be using something else?

回答1:

You can use this lookahead based regex:

(.{2,})(?=.*?\1)

RegEx Demo

Explanation:

.{2,}     # any 2 or more characters
(.{2,})   # group them into captured group #1
(?=...)   # positive lookahead
(?=.*?\1) # make sure at least one occurrence of captured group #1

来源：https://stackoverflow.com/questions/30239626/matching-when-an-arbitrary-pattern-appears-multiple-times