I\'m looking for a browser extension (Firefox, Chrome) allowing to replace a Javascript file on a live Web site to do some testing/hacking.
Basically, it should take a U
Disclaimer: I'm the author of the software :-)
A different approach that might suit your usecase better is to use a RoboHydra-based development proxy. The idea here would be that you want to keep ALL Javascript files in your machine, and use another server simply as a backend. It's great for eg. front-end developers that don't want to have the whole backend installed in their machines.
You can see the documentation, tutorials and such at http://robohydra.org/, and have an article describing exactly that usecase at http://dev.opera.com/articles/view/robohydra-a-new-testing-tool-for-client-server-interactions/.
However, as of now it can't proxy to HTTPS URLs, but that should be a trivial change that I intend to do soon anyway.