book

Mastering JavaScript Functional Programming - Third Edition

by Federico Kereki

April 2023

Intermediate to advanced

614 pages

12h 41m

English

Packt Publishing

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Third EditionContributorsAbout the authorAbout the reviewers
Who this book is forWhat this book coversTo get the most out of this bookDownload the example code filesDownload the color imagesConventions usedGet in touchShare Your ThoughtsDownload a free PDF copy of this book
What is functional programming?Theory versus practiceA different way of thinkingFP and other programming paradigmsWhat FP is notWhy use FP?What we needWhat we getNot all is goldIs JavaScript functional?JavaScript as a toolGoing functional with JavaScriptKey features of JavaScriptHow do we work with JavaScript?Using transpilersWorking onlineA step further – TypeScriptTestingSummaryQuestions
Our problem – doing something only onceSolution 1 – hoping for the best!Solution 2 – using a global flagSolution 3 – removing the handlerSolution 4 – changing the handlerSolution 5 – disabling the buttonSolution 6 – redefining the handlerSolution 7 – using a local flagA functional solution to our problemA higher-order solutionTesting the solution manuallyTesting the solution automaticallyProducing an even better solutionSummaryQuestions
All about functionsOf lambdas and functionsArrow functions – the modern wayFunctions as objectsUsing functions in FP waysInjection – sorting it outCallbacks and promisesContinuation-passing stylePolyfillsStubbingImmediate invocation (IIFE)SummaryQuestions
Pure functionsReferential transparencySide effectsAdvantages of pure functionsImpure functionsAvoiding impure functionsIs your function pure?Testing – pure versus impureTesting pure functionsTesting purified functionsTesting impure functionsSummaryQuestions
TransformationsReducing an array to a valueApplying an operation – map()Dealing with arrays of arraysMore general loopingLogical HOFsFiltering an arraySearching an arrayHigher-level predicates – every() and some()Checking negatives – none()Working with async functionsSome strange behaviorsAsync-ready loopingWorking with parallel functionsUnresponsive pagesA frontend workerA backend workerWorkers, FP styleLong-living pooled workersSummaryQuestions
Wrapping functions – keeping behaviorLoggingTiming functionsMemoizing functionsAltering a function’s behaviorDoing things once, revisitedLogically negating a functionInverting the resultsArity changingThrottling and debouncingChanging functions in other waysTurning operations into functionsTurning functions into promisesGetting a property from an objectDemethodizing – turning methods into functionsMethodizing – turning functions into methodsFinding the optimumSummaryQuestions
A bit of theoryCurryingDealing with many parametersCurrying by handCurrying with bind()Partial applicationPartial application with arrow functionsPartial application with closuresPartial curryingPartial currying with bind()Partial currying with closuresFinal thoughtsVariable number of parametersParameter orderBeing functionalSummaryQuestions
PipeliningPiping in Unix/LinuxRevisiting an exampleCreating pipelinesDebugging pipelinesPointfree styleChaining and fluent interfacesAn example of fluent APIsChaining method callsComposingSome examples of compositionComposing with higher-order functionsTransducingComposing reducersGeneralizing for all reducersTesting connected functionsTesting pipelined functionsTesting composed functionsTesting chained functionsTesting transduced functionsSummaryQuestions

Using recursionThinking recursivelyHigher-order functions revisitedSearching and backtrackingMutual recursionOdds and evensDoing arithmeticRecursion techniquesTail call optimizationContinuation-passing styleTrampolines and thunksRecursion eliminationSummaryQuestions
Going the straightforward JavaScript wayMutator functionsConstantsFreezingCloning and mutatingGetters and settersLensesPrismsCreating persistent data structuresWorking with listsUpdating objectsA final caveatSummaryQuestions
Understanding design patternsDesign pattern categoriesDo we need design patterns?Object-oriented design patternsFacade and AdapterDecorator or WrapperStrategy, Template, and CommandDependency InjectionObservers and reactive programmingOther patternsFunctional design patternsSummaryQuestions
Specifying data typesSignatures for functionsOther data type optionsBuilding containersExtending current data typesContainers and functorsMonadsFunctions as data structuresBinary trees in HaskellFunctions as binary treesSummaryQuestions
Chapter 1, Becoming Functional – Several QuestionsChapter 2, Thinking Functionally – A First ExampleChapter 3, Starting Out with Functions – A Core ConceptChapter 4, Behaving Properly – Pure FunctionsChapter 5, Programming Declaratively – A Better StyleChapter 6, Producing Functions – Higher-Order FunctionsChapter 7, Transforming Functions – Currying and Partial ApplicationChapter 8, Connecting Functions – Pipelining, Composition, and MoreChapter 9, Designing Functions – RecursionChapter 10, Ensuring Purity – ImmutabilityChapter 11, Implementing Design Patterns – The Functional WayChapter 12, Building Better Containers – Functional Data Types
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Overview

"Mastering JavaScript Functional Programming" dives deep into the world of functional programming using JavaScript and TypeScript. You'll go from understanding the core principles of functional paradigms to applying them effectively to create robust, clean, and maintainable code. Packed with in-depth explanations and practical examples, this book equips you with the tools needed for building concise and efficient applications.

What this Book will help me do

Understand the differences between functional and object-oriented programming and when to use each.
Learn how to write and test pure functions to improve program modularity and reliability.
Master the use of closures, immutability, and declarative coding for developing maintainable applications.
Apply recursion in functional programming to solve complex programming problems naturally.
Gain expertise in using functional programming principles to improve code efficiency and compatibility with TypeScript.

Author(s)

Federico Kereki is an accomplished software engineer and instructor with years of experience in JavaScript and functional programming. He has a passion for teaching technical concepts in accessible and engaging ways, making him an ideal guide to mastering functional programming. His approach is hands-on and example-driven, enabling learners to apply what they learn in real situations.

Who is it for?

This book is perfect for JavaScript and TypeScript developers seeking to elevate their programming capabilities. Whether you're developing for the frontend with frameworks like React, Angular, or Vue, or working on backend applications with Node.js or Deno, this book offers valuable insights. If you want to leverage functional programming for cleaner, more robust code, this book is for you.