[codygman]

> it's simpler to directly call the right function, rather than over-engineering things with a short-lived intermediary representation.

That intermediary representation can enforce that your input is valid. Then you can create functions based on that intermediary representation and act as if your data is valid because it is.

The intermediary representation can also ensure you cover all cases if your states are encoded with sum/product types thanks to exhaustiveness checking in supported languages.

> I'm not trying to shoot down Haskell here, I really wish someone will point to something I'm missing and make it click. But right now it just looks like over-engineering that JS could do but chooses not to.

JS can't turn runtime errors into compile time errors because it doesn't have a compiler or a powerful type system. In fact it has a very weak/dynamic type system.