CODEWITHSUNDEEP
javascriptregex
kittu
kittu

Reputation: 7018

Understanding regex of non capturing group

I am little confused understanding the regex pattern below from this link:

(?:x)

Matches 'x' but does not remember the match. The parentheses are called non-capturing parentheses, and let you define subexpressions for regular expression operators to work with. Consider the sample expression /(?:foo){1,2}/. If the expression was /foo{1,2}/, the {1,2} characters would apply only to the last 'o' in 'foo'. With the non-capturing parentheses, the {1,2} applies to the entire word 'foo'. For more information, see Using parentheses below.

I am not able to understand these two points:

  1. Consider the sample expression /(?:foo){1,2}/. If the expression was /foo{1,2}/, the {1,2} characters would apply only to the last 'o' in 'foo'.

  2. With the non-capturing parentheses, the {1,2} applies to the entire word 'foo'

Upvotes: 0

Views: 46

Answers (1)

Tim Biegeleisen
Tim Biegeleisen

Reputation: 522636

Actually, as far as I know, the non capturing group has nothing to do with your immediate question, and both of the following patterns would match the same things:

/(?:foo){1,2}/
/(foo){1,2}/

The parentheses tell the regex engine that you want the quantity rule {1,2} to apply to the entire quantity. Without the parentheses, the quantity defaults to applying to the immediately preceding character o:

/foo{1,2}/

This would match foo and fooo.

Upvotes: 1

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