[samhh]

It's a bit high level in that the benefits aren't obvious until you buy into other functional concepts, but basically it's that Options can be layered i.e. Option<Option<string>> is possible. If you just use ordinary union types there's no way to express that.

As an aside, TypeScript is very unsafe by default, and still relatively unsafe with strict mode enabled. Stringent fp-ts usage bypasses these issues.

[golergka]

> still relatively unsafe with strict mode enabled

Is it? I have been using Typescript more and more these last few years, and lately haven't really experienced any issues where it's type system failed me.

To clarify, I'm not trying to argue against your point, genuinely curious to learn if fp-ts can really improve my code quality in production.

[samhh]

It is, for example accessing an array or record doesn't unionise the returned value type with undefined, though this particular gaping hole of unsafety is being addressed in 4.1 with a new flag.

Beyond that there's functions that throw/reject doing so outside the type system, something solved by Either/Option/similar types in fp-ts.

The biggest benefit of fp-ts though is that it makes you think functionally. If you're dead set against that, then there are plenty of other libraries that give you types/wrappers like these without having to use pipe/flow (two functions you'll want to use before anything else in fp-ts).