Maybe this architecture approach would be challenging in Java or Go, but the style of immutable data, don’t go crazy wrapping stuff in classes is very doable in most languages. We enforce “no mutation of data you did not just instantiate” at Notion, and use TypeScript’s powerful type system with tagged union types to ensure exhaustive handling of new variants which I really miss in languages that don’t have it (go).

I guess the major advantage for Closure with this style is the “persisted” data structures end up sharing some bytes behind the scenes - it’s nice the language is explicitly situated around this style, rather than TypeScript’s chaotic Wild West kitchen sink design. What I don’t understand the advantage for “state management”. Like, you build a new state object, and then mutate some pointer from prevState to nextState… that’s what everyone else is doing too.

There are times though when it’s nice to switch gears from function-and-data to an OO approach when you need to maintain a lot of invariants, interior mutability has substantial performance advantages, or you really want to make sure callers are interpreting the data’s semantics correctly. So our style has ended up being “functional/immutable business logic and user data” w/ “zero inheritance OO for data structures”.

Whenever I read some open source TypeScript code that’s using the language like it’s Java like `class implements ISomething` ruining cmd-click go to method or an elaborate inheritance hierarchy it makes me sad.