Overriding javascripts/hmtl/css/ etc... files in projects

I'm trying to build a web library that is supposed to be an infrastructure to my other projects.
In those other projects I'll be overriding some of the scripts, styles and other components, but some of the functionality should stay the same and not be overriden. I'd like NOT to copy all the files to every project, but packing them and extracting the files in production will be ok.

What is the best/standard way to do it?