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Typed functional programming in TypeScript

fp-ts provides developers with popular patterns and reliable abstractions from typed functional languages in TypeScript.

Get started


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
2.0.x+ 3.5+
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.