This is a terribly exciting book.
Despite its ignominious origins as a “Java-lite” scripting language, intended to be embedded inline in HTML documents to allow a minimum modicum of interactivity‚ JavaScript has always been one of the most essentially flexible languages for general purpose programming.
You can sketch, smudge, and draft bits of code in JavaScript, while pushing and twisting the language in the direction that best suits your particular style. The reason that this is more natural in JavaScript than in other, more rigid languages is due to the small set of strong core ideas that lie at the heart of JavaScript: Everything is an object (everything is a value) to an even greater extent than in famously object-oriented languages like Ruby and Java. Functions are objects, are values. An object may serve as prototype (default values) for any other object. There is only one kind of function, and depending on how you employ it, it can either serve as a pure function, a mutating procedure, or as a method on an object.
JavaScript enables, but does not enforce, many different programming styles. In the early days, we tended to bring our traditional expectations and “best” practices with us when we started to learn to write JavaScript. Naturally this led to much JavaScript resembling Java without the omnipresent types or even with the types still there, just living inside of annotation comments above each method. Gradually, experiments were made: folks started generating functions at runtime, working with immutable data structures, creating different patterns for object-orientation, discovering the magic of chaining APIs, or extending built-in prototypes with custom functionality.
One of my favorite recent developments is the enthusiastic embrace of functional programming ideas as appropriate tools for building rich JavaScript applications. As we move beyond form validation and DOM animation towards full-featured apps, where the JavaScript in your codebase might be getting up to any manner of hijinks in any particular problem space, functional ideas are similarly moving beyond the basic callback, and towards more interesting arenas, such as:
Building out a large API by partially applying a core set of functions with arguments in different configurations.
Using recursive functions to smooth the gap between actions that need to occur for a period of time, and events coming in rapid-fire off the event loop.
Structuring a piece of complex business logic as a pipeline of mutation-free changes that can later be plugged-into and pulled apart.
You’re reading the ideal book with which to explore this territory. In the following nine chapters (and two appendixes), your friendly tour guide and resident mad scientist, Michael Fogus, breaks down functional programming into its basic atoms, and builds it back up again into edifices of terrifying cleverness that will leave you wondering. It’s rare that a programming book can take you by surprise, but this one will.
Enjoy.
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