ts-option
Scala like Option type for TypeScript
declarative-optional
A Declarative way to deal with null , undefined and promises via optional and streams
monads-co
An implementation of Haskell's type classes in TS
@efflore/flow-sure
FlowSure - a Result monad in TypeScript. Data types Ok, Nil, Err with maybe(), result(), asyncResult() and flow() functions.