Book Image

Mastering JavaScript Functional Programming

By : Federico Kereki
Book Image

Mastering JavaScript Functional Programming

By: Federico Kereki

Overview of this book

Functional programming is a programming paradigm for developing software using functions. Learning to use functional programming is a good way to write more concise code, with greater concurrency and performance. The JavaScript language is particularly suited to functional programming. This book provides comprehensive coverage of the major topics in functional programming with JavaScript to produce shorter, clearer, and testable programs. You’ll delve into functional programming; including writing and testing pure functions, reducing side-effects, and other features to make your applications functional in nature. Specifically, we’ll explore techniques to simplify coding, apply recursion for loopless coding, learn ways to achieve immutability, implement design patterns, and work with data types. By the end of this book, you’ll have developed the JavaScript skills you need to program functional applications with confidence.
Table of Contents (22 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback
Connecting Functions - Pipelining and Composition
Answers to Questions


Composing is quite similar to pipelining, but has its roots in mathematical theory. The concept of composition is simple - a sequence of function calls, in which the output of one function is the input for the next one - but the order is reversed from the one in pipelining. In the latter, the first function to be applied is the leftmost one, but in composition, you start with the rightmost one. Let's investigate this a bit more.

When you define the composition of, say, three functions, as (f∘ g∘ h) and apply it to x, this is equivalent to what you would write as f(g(h(x))). It's important to note that, as with pipelining, the arity of the first function to be applied can be anything, but all the other functions must be unary. Also, apart from the difference as to the sequence of function evaluations, composing is an important tool in FP, because it also abstracts implementation details (putting your focus on what you need to accomplish, rather than on the specific details for achieving...