Functional JavaScript

About the book

Michael Fogus wrote Functional JavaScript for programmers who already know the language and want to use functions more deliberately. The book treats functions as the central building block and shows how to organize code around them instead of around objects and mutable state.

The premise is practical. Fogus works through the ideas that make functional code possible in JavaScript, including higher-order functions, closures, and the treatment of functions as values that can be passed around and composed. He also addresses the parts of the language that complicate a functional approach, such as its handling of scope and its mutable data structures.

How to read it

Approach the book as a set of arguments about how to structure code, supported by examples. The examples carry much of the weight, so read them actively and try the patterns in a small program of your own. Fogus builds ideas in sequence, and skipping ahead tends to make later sections harder than they need to be.

The difficulty sits in the middle. Readers comfortable with JavaScript syntax will follow the early material, while the discussion of closures, recursion, and avoiding shared state asks for patience. Expect to reread sections. The book rewards slow reading more than fast completion.

Who it suits

This suits developers who write JavaScript regularly and want a clearer mental model of functions as values. It helps readers who have heard functional programming praised and want to see what it means in a language they already use. Programmers coming from object-oriented habits will find the contrast useful, and those preparing to work with functional libraries will get grounding in the ideas behind them.

Reading considerations

Some examples use idioms that later versions of JavaScript handle differently, so be ready to translate older patterns into current syntax. Readers looking for a broad tour of the language should look elsewhere; this is a focused treatment of one style.