Changing things to be more modular in order to make it more manageable is a great idea. But the problem is still that you cannot make any such change to existi

Changing things to be more modular in order to make it more manageable is a great idea. But the problem is still that you cannot make any such change to existing large Javascript codebase, because you don't have the kind of tools that you need in order to do so with any confidence that you won't have an enormous amount of uncaught runtime errors when you're done. This is what a static type system gives you.