Functional programming in TypeScript

Typed functional programming in TypeScript

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

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

Inspired by

- Haskell
- PureScript
- Scala

Table of contents

- Installation
- TypeScript compatibility
- Documentation
- Development
- License

Installation

To install the stable version:

``
npm install fp-ts
`

Make sure to always have a single version of fp-ts 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 fp-ts (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.

| fp-ts version | required typescript version |
| --------------- | ----------------------------- |
| 1.15.x+ | 3.1+ |
| <= 1.14.4 | 2.8+ (\*) |

(\*) If you are running < typescript@3.0.1 you have to polyfill the unknown` type. You can use unknown-ts as a polyfill.

Documentation

- Docs
- Tutorial
- Ecosystem
- API Reference

Development

- Code conventions

License

The MIT License (MIT)