there's no way to define an interface an implementation has to conform to

I had this view too once.. it took me a long time to see it, but when I finally realised that trying to twist JavaScript to work how I thought it should work (heavily typed, classic OO architecture), and embrace how it actually works (loosely typed, prototypal) it eventually made JavaScript a joy to work with.

I don't mean that in a "understand the in's and out's of the language" sense, I knew that very well at the time. I mean from the perspective of how I structure things and approach problems.

I still prefer heavily typed classic OO languages, that's just how I am.. but those languages started to feel more and more clunky as I got used to my new way of working with JavaScript, rather than the other-way-round as it was before. It's interesting that those languages are now implementing more and more features from JavaScript.. closures, automatic type definition, inline object definition, etc. and I'm seeing a "hash of objects" as parameters with validators lot more these days.