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

This is an equivalent solution to Tim Pietzcker's answer (see also comments of same answer):

^(?!.*filename\.js$).*\.js$

It means, match *.js except *filename.js.

To get to this solution, you can check which patterns the negative lookbehind excludes, and then exclude exactly these patterns with a negative lookahead.