Use JavaScript regex groups to match if other groups dont match before it

Can I use a javascript regex to capture if the first group(s) don't capture?

Here i have two(three) capturing groups:

/("[^\n"]*")|("[^\n"]*(?:\n|$))/g

What i would like is to place anything that did not match in the first two, in another like so

/("[^\n"]*")|("[^\n"]*(?:\n|$))|(<CATCH ANYTHING ELSE HERE>)/g

Is this possible?

In practice, this would mean always matching the entire string, but being able to segment it.

(I am building a code editor, trying to parse strings in the code).

I tried adding (.*) but that seemed to always catch "before" the other two.

EDIT:

To simplify, lets say I want to segment a string into two groups:

1. All characters that are a
2. All characters that are not a

Given the regex /(a)|(^\1)/g, I would assume the entire string would match but this is not the case. Why? In more complex cases I assume using backreferences is better?

This expression does the job:

(regex1)|(regex2)|((?:(?!regex1|regex2).)*)

where:

• regex1 is your first regex
• regex2 is your second regex
• the last group captures a single character repeated until one of the first two regexes is matched. In particular, (?!...) is called negative lookahead.

In your example, you can use /(a)|((?:(?!a).)*)/g.

P.S. Note that your regex is wrong also because ^ matches the beginning of a string!

P.P.S. As pointed out in comments, backreference \1 won't work, because it refers to the actual text matched, not to the expression that catched it.