Functional programming in TypeScript

Introduction

@jvlk/fp-tsm is a fork of fp-ts that supports ESM. If you need CJS support you should continue to use fp-ts. While fp-tsm has been updated to work with modern JS and TS, you should really consider using effect for new projects. fp-ts is now a part of effect and you will find much better support over there.

fp-tsm is a library for _typed functional programming_ in TypeScript.

fp-tsm aims to allow developers to use _popular patterns and abstractions_ that are available in most functional languages. For this, it includes the most popular data types, type classes and abstractions such as Option, Either, IO, Task, Functor, Applicative, Monad to empower users to write pure FP apps and libraries built atop higher order abstractions.

A distinctive feature of fp-tsm with respect to other functional libraries is its implementation of Higher Kinded Types>), which TypeScript doesn't support natively.

Inspired by

- Haskell
- PureScript
- Scala

Installation

To install the stable version:

``
npm install @jvlk/fp-tsm
`

Make sure to always have a single version of fp-tsm installed in your project. Multiple versions are known to cause tsc to hang during compilation. You can check the versions currently installed using npm ls @jvlk/fp-tsm (make sure there's a single version and all the others are marked as deduped).

TypeScript compatibility

Strictness – This library is conceived, tested and is supposed to be consumed by TypeScript with the strict flag turned on.

@jvlk/fp-tsm is tested with TypeScript V5 and up and older versions might not work.

Original fp-ts Documentation

These are docs for the original fp-ts which should cover what you need to use fp-tsm.

New docs are under development for fp-tsm`. I'm hoping to eventually just use JSR for docs.

Disclaimer. Teaching functional programming is out of scope of this project, so the documentation assumes you already know what FP is.

- Docs
- Learning Resources
- Ecosystem
- API Reference
- version 2.x (current)
- version 1.x

Development

- Code conventions

License

The MIT License (MIT)