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Functional-Light JavaScript


It's no secret that I am a Functional Programming nut. I evangelize functional ideas and languages wherever I can, try to read the latest academic papers, study abstract algebra in my spare time…the works. Even in JavaScript, I refuse to write an impure statement, which is what led to writing Professor Frisby's Mostly Adequate Guide to Functional Programming. Yep, full on, dogmatic zealot.

I was not always this way… I was once obsessed with objects. I loved modeling the "real world". I was the inventor of synthetic automatons, tinkering through the night with masterful precision. The creator of sentient puppets, fingers dancing on the keyboard to give them life -- a real 1337 h4x0r Geppetto. Yet, after 5 solid years of writing object-oriented code, I was never quite satisfied with the outcome. It just never worked out well for me. I felt like a lousy programmer. I even lost faith that a simple, flexible codebase of decent scale was possible.

I figured I'd try something different: Functional Programming. I began to dabble with functional ideas in my everyday codebase, and much to my coworkers' dismay, hadn't the slightest clue what I was doing. The code I wrote in those days was awful. Atrocious. Digital sewage. The reason was a lack of clear vision or goal on what I was even trying to accomplish. My Jiminy-Coding-Cricket, if you like, was not there to guide me. It took a long time and a lot of garbage programs to figure out how to FP.

Now, after all that messy exploration, I feel that pure Functional Programming has delivered on its promise. Readable programs do exist! Reuse does exist! I no longer invent, but rather discover my model. I've become a rogue detective uncovering a vast conspiracy, cork board pinned full of mathematical evidence. A digital-age Cousteau logging the characteristics of this bizarre land in the name of science! It's not perfect and I still have a lot to learn, but I've never been more satisfied in my work and pleased with the outcome.

Had this book existed when I was starting out, my transition into the world of Functional Programming would have been much easier and less destructive. This book is two-fold (right and left): it will not only teach you how to use various constructs from FP effectively in your daily code, but more importantly, provide you with an aim; guiding principles that will keep you on track.

You will learn Functional-Light: A paradigm that Kyle has pioneered to enable declarative, Functional Programming while providing balance and interop with the rest of the JavaScript world. You will understand the foundation which pure FP is built upon without having to subscribe to the paradigm in its entirety. You will gain the skills to practice and explore FP without having to rewrite existing code for it to work well together. You can take a step forward in your software career without backtracking and wandering aimlessly as I did years ago. Coworkers and colleagues rejoice!

Kyle is a great teacher known for his relentless pursuit of the whole picture, leaving no nook or cranny unexplored, yet he maintains an empathy for the learner's plight. His style has resonated with the industry, leveling us all up as a whole. His work has a solid place in JavaScript’s history and most people's bookmarks bar. You are in good hands.

Functional Programming has many different definitions. A Lisp programmer's definition is vastly different from a Haskell perspective. OCaml's FP bears little resemblance to the paradigm seen in Erlang. You will even find several competing definitions in JavaScript. Yet there is a tie that binds -- some blurry know-it-when-I-see-it definition, much like obscenity (indeed, some do find FP obscene!) and this book certainly captures it. The end result might not be considered idiomatic in certain circles, but the knowledge acquired here directly applies to any flavor of FP.

This book is a terrific place to begin your FP journey. Take it away, Kyle...

-Brian Lonsdorf (@drboolean)

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