TL;DR
FP-pack is a lightweight TypeScript toolkit offering pipe and pipeAsync-based function composition, a SideEffect pattern for declarative error/side-effect handling, and lazy stream utilities. It ships as a zero-dependency, tree-shakeable collection with TypeScript-first types and an optional AI skills file to guide coding assistants.
What happened
A new utility collection called fp-pack has been published as a practical functional toolkit for JavaScript and TypeScript projects. Implemented in TypeScript, the library centers on pipe (sync) and pipeAsync (async) composition primitives and aims to keep functional code approachable by avoiding heavy abstractions and pervasive wrapper types. fp-pack provides a SideEffect pattern and dedicated pipeSideEffect variants to let pipelines short-circuit on errors or other side effects without littering code with error plumbing; strict variants exist for effect unions. The package includes curried helpers, immutable-by-default utilities, stream/* helpers for lazy iterable processing, and common helpers for arrays, objects, strings, math, and async flows. It is distributed with full documentation, installation instructions via npm/pnpm/yarn, and an optional AI agent skills file intended to configure assistants to use fp-pack conventions.
Why it matters
- Makes functional composition more accessible by centering on pipe/pipeAsync and curried helpers rather than abstract effect types.
- TypeScript-first design aims to provide robust type inference for real-world code while remaining usable from plain JavaScript.
- Lazy stream helpers help conserve memory when working with large datasets by processing items only as needed.
- Zero dependencies and tree-shakeable modules reduce bundling overhead and let projects pick just the utilities they need.
Key facts
- fp-pack is written in TypeScript and usable from both JavaScript and TypeScript projects.
- Primary composition functions are pipe (synchronous) and pipeAsync (asynchronous).
- SideEffect-aware pipelines include pipeSideEffect, pipeAsyncSideEffect and strict variants for strict effect unions.
- Stream/* helpers provide lazy iterable processing for memory-conscious operations on large datasets.
- All multi-argument utilities are curried or behave like curried functions to support partial application in pipes.
- Utilities prioritize immutability and pure functions by default; exceptions are explicitly named (e.g., tap, log).
- The package is zero-dependency and designed to be tree-shakeable.
- An optional AI agent skills file is included to guide coding assistants to use fp-pack patterns; the documentation explains how to copy that file into assistant skills directories.
What to watch next
- Community adoption and real-world usage patterns — not confirmed in the source
- Ecosystem integrations or wrappers for popular frameworks and libraries — not confirmed in the source
- Ongoing maintenance, release cadence, and responsiveness to issues or PRs — not confirmed in the source
Quick glossary
- pipe / pipeAsync: Composition helpers that build a left-to-right pipeline of functions; pipeAsync is the async-aware version.
- currying: Transforming a multi-argument function into a sequence of single-argument functions to enable partial application.
- SideEffect: A pattern or container used to represent errors or side effects so pipelines can short-circuit or handle them declaratively.
- lazy stream (iterable): An approach that processes items on demand rather than materializing a whole collection in memory, useful for large datasets.
- tree-shakeable: A library design that allows bundlers to drop unused code so consumers only include the functions they import.
Reader FAQ
Is fp-pack written in TypeScript and usable from JavaScript?
Yes. The library is implemented in TypeScript and is said to work seamlessly in both JavaScript and TypeScript projects.
How do I install fp-pack?
Installation options shown in the docs are: npm install fp-pack, pnpm add fp-pack, or yarn add fp-pack.
How does fp-pack handle errors and side effects?
It uses a SideEffect pattern and provides pipeSideEffect / pipeAsyncSideEffect (and strict variants) to short-circuit pipelines and handle side effects declaratively.
Does fp-pack rely on monads or heavy functional abstractions?
The source emphasizes avoiding heavy abstractions and wrapper types; it favors pipe-centric composition and the SideEffect pattern instead.
fp-pack A practical functional toolkit for JavaScript and TypeScript. Written in TypeScript with full type safety, fp-pack works seamlessly in both JavaScript and TypeScript projects. fp-pack is a focused collection…
Sources
- Show HN: FP-pack – Functional pipelines in TypeScript without monads
- fp-ts Using async function in middle of pipe
- Functional Programming in TypeScript using the fp-ts library
- Intro to Functional Programming in TypeScript with FP-TS
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