// the find
getify/Functional-Light-JS
Pragmatic, balanced FP in JavaScript. @FLJSBook on twitter.
A free online book by Kyle Simpson (of 'You Don't Know JS' fame) teaching functional programming concepts in JavaScript without the academic Haskell baggage. It's aimed at working JS developers who want to write more predictable, testable code without committing to a full FP library or spending a year learning category theory.
The 'light' framing is genuine — Simpson deliberately skips monads and type theory until you're ready, focusing instead on composition, pure functions, and immutability as practical tools you can apply Monday morning. The chapter on closure vs. object is one of the better treatments of that tension in JS writing. The final chapter builds a real stock ticker app using every technique covered, so the concepts land in context rather than in isolation. Foreword by Brian Lonsdorf gives it credibility in the FP community.
Last updated in 2023 but the core content was written 2016-2018 — it predates widespread async/await patterns and doesn't address how FP principles interact with modern React or other frameworks that your team is probably using. It's a book hosted on GitHub, not a library or a tool, so there's nothing to run or adopt directly; you're buying a reading experience. The CC BY-NC-ND license blocks remixing or adaptation, which limits how instructors or teams can use it internally.