TypeScript를 활용한 함수형 프로그래밍 온보딩
1. CH04_05. Option 소개
- ADT tagged union
- TypeScript: Documentation - Narrowing
export const isSome = <A>(oa: Option<A>): oa is Some<A> => oa._tag === "Some"; export const isNone = <A>(oa: Option<A>): oa is None => oa._tag === "None";