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

Logical higher-order functions

Up to now, we have been using higher-order functions to produce new results, but there are also some other functions that produce logical results, by applying a predicate to all the elements of an array.


A bit of terminology: the word predicate can be used in several senses (as in Predicate Logic) but for us, in computer science, we adopt the meaning a function that returns true or false. OK, this isn't a very formal definition, but it's enough for our needs. For example, we will filter an array depending on a predicate, and that just means that we get to decide which elements are included or excluded depending on the result of the predicate.

Using these functions implies that your code will become shorter: you can, with a single line of code, get the results corresponding to the whole set of values.

Filtering an array

A common need is having to filter the elements of an array according to some condition. The .filter() method lets you inspect each element of...