Q:

How can I reverse this Regex?

I've got a successful match on:
/^\/?build\/(.+\.coffee|.+\.sass|.+\.erb)$/

Now I want to find all files under /build/ that DON'T match either of those extensions. I think I can do this with negative look-ahead but I can't seem to get it working.
Any thoughts?

A:

if you find all files under /build/ and DON'T match either of those extensions,you'd better use "?!" to except string,for example:
^\/?build\/(?:(?!\.coffee|\.sass|\.erb).)*$

