CODEWITHSUNDEEP
regex
gorn
gorn

Reputation: 5340

How can enclosing regexp in group change the result?

On a string 'abbc'

This regexp /(.)\1*/g gives 3 matches ('a','bb' and 'c').

Very similar regexp /((.)\1*)/g gives 4 matches (('a','b', 'b' and 'c').

I always assumed, that the outside group does not and can not change the result. How that is even possible?

See https://regex101.com/r/5fX9My/1

Upvotes: 0

Views: 31

Answers (1)

41686d6564
41686d6564

Reputation: 19651

Your second pattern doesn't match the same as the first one. When you enclose your pattern in a capturing group, that group becomes group #1. So, in your first pattern, \1 is a backreference for (.) while in the second pattern, \1 is a backreference for the outer group.

To create a pattern that's identical to the first one but with an extra outer group, you should use:

((.)\2*)

Demo.

Upvotes: 1

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