Even if you don't have source to show, if your back-end experience includes Node and you can converse about it freely and intelligently, I think you'll be fine.

Maybe you could write a blog post examining some confusing element of Node architecture? Or walking people though a simple JS MVC PoC? Basically just provide some sort of technical copy (on your resume/linkedIn/wherever)that shows you understand some of the basic features of JS development (closures, callbacks, prototypical inheritance - which sounds like its all old hat for you). With your other projects and experience, I think that would be enough.