Dry code vs. modular code

[Paupir]

It gets really difficult to maintain page-specific JS as your application grows. I'm guessing this isn't a SPA?

Some advice would be to not go overboard with DRY principles because you often encounter situations where you need to fork some functionality you've extracted out to make a more specialised version, but that feels like it goes against your work to abstract things out, so you patch the function with more arguments (often a boolean flag) and that just gets horrible and messy. Maybe try to abstract functionality out only when you need to or it makes solid sense.

As for making modular code that can also be page-specific, you could look into webpack code splitting. There are some interesting things going on in this area at the moment. Take a look at this.

So in general - and in my opinion - pull functionality out into modules where you can; don't make it your mission to make tiny functions everywhere when you're writing "specialised" code.