My world changed when I started thinking in a strongly typed way (not just using string and number) and representing state changes as different types rather than interpreting than through property values. Once you do that then your code becomes mapping from one type to the next.
For example, if `type ShoppingCart = EmptyCart | LoadedCart` then `addToCart` is just a map from `ShoppingCart` to `LoadedCart`. It makes invalid states impossible to represent and flows become clearer. Add in good FP and composition becomes easier.
I am not against types but I do find typescript’s type system to be deficient. Additionally, functional programming is not incompatible with type systems but typescript’s type system in particular makes it more difficult.
Several of the terrible typescript projects I referred to still used property values to represent state (like your example). Just because every definition has a type doesn’t make it good code. Shitty typed code is still shitty code. My concern is that many in our industry conflate typescript with quality and stop there.
I'm curious which part you find deficient? It's biggest downside is probably being Turing complete but that doesn't make it deficient, rather it's too easy for devs to code incomprehensible types with it.
For example, if `type ShoppingCart = EmptyCart | LoadedCart` then `addToCart` is just a map from `ShoppingCart` to `LoadedCart`. It makes invalid states impossible to represent and flows become clearer. Add in good FP and composition becomes easier.