javascript regex - look behind alternative?

Question

Here is a regex that works fine in most regex implementations:

(?

This matches .js for a string which ends with .js exc

Answer 1

Let's suppose you want to find all int not preceded by unsigned:

With support for negative look-behind:

(?

Without support for negative look-behind:

((?!unsigned ).{9}|^.{0,8})int

Basically idea is to grab n preceding characters and exclude match with negative look-ahead, but also match the cases where there's no preceeding n characters. (where n is length of look-behind).

So the regex in question:

(?

would translate to:

((?!filename).{8}|^.{0,7})\.js$

You might need to play with capturing groups to find exact spot of the string that interests you or you want't to replace specific part with something else.