Composing Software
Composing Software
An Exploration of Functional Programming and Object Composition in JavaScript
About the Book
All software design is composition: the act of breaking complex problems down into smaller problems and composing those solutions. Most developers have a limited understanding of compositional techniques. It's time for that to change.
In "Composing Software", Eric Elliott shares the fundamentals of composition, including both function composition and object composition, and explores them in the context of JavaScript. The book covers the foundations of both functional programming and object oriented programming to help the reader better understand how to build and structure complex applications using simple building blocks.
You'll learn:
- Functional programming
- Object composition
- How to work with composite data structures
- Closures
- Higher order functions
- Functors (e.g., array.map)
- Monads (e.g., promises)
- Transducers
- Lenses
All of this in the context of JavaScript, the most used programming language in the world. But the learning doesn't stop at JavaScript. You'll be able to apply these lessons to any language. This book is about the timeless principles of software composition and its lessons will outlast the hot languages and frameworks of today. Unlike most programming books, this one may still be relevant 20 years from now.
This book began life as a popular blog post series that attracted hundreds of thousands of readers and influenced the way software is built at many high growth tech startups and fortune 500 companies.
About the Author
Table of Contents
- Thank You
-
Composing Software: An Introduction
- You Compose Software Every Day
- Conclusion
-
The Dao of Immutability (The Way of the Functional Programmer)
- Forward
-
The Rise and Fall and Rise of Functional Programming (Composable Software)
- The Rise of Functional Programming
- The Fall of Functional Programming
- The Rise of Functional Programming
- Functional Programming Has Always Been Alive and Well
- Why Learn Functional Programming in JavaScript?
-
Pure Functions
- What is a Function?
- Mapping
- Pure Functions
- The Trouble with Shared State
- Same Input, Same Output
- No Side Effects
- Conclusion
-
What is Functional Programming?
- Pure Functions
- Function Composition
- Shared State
- Immutability
- Side Effects
- Reusability Through Higher Order Functions
- Containers, Functors, Lists, and Streams
- Declarative vs Imperative
- Conclusion
-
A Functional Programmer’s Introduction to JavaScript
- Expressions and Values
- Types
- Destructuring
- Comparisons and Ternaries
- Functions
- Currying
- Function Composition
- Arrays
- Method Chaining
- Conclusion
- Higher Order Functions
-
Curry and Function Composition
- What is a curried function?
- What is a partial application?
- What’s the Difference?
- What is point-free style?
- Why do we curry?
- Trace
- Curry and Function Composition, Together
- Conclusion
-
Abstraction & Composition
- Abstraction is simplification.
- Abstraction in Software
- Abstraction through composition
- How to Do More with Less Code
- Conclusion
- Reduce
- Reduce is Versatile
- Conclusion
-
Abstract Data Types and the Software Crisis
- Common ADT Examples
- Why ADTs?
- History of ADTs
- Specifications for ADTs
- Stack ADT Example
- Concrete Implementations
- Conclusion
- Glossary
-
Functors & Categories
- Why Functors?
- Functor Laws
- Category Theory
- Build Your Own Functor
- Curried Map
- Conclusion
-
Monads
- You’re probably already using monads.
- What Monads are Made of
- Building a Kleisli Composition Function
- The Monad Laws
- Conclusion
-
The Forgotten History of OOP
- The Big Idea
- The Essence of OOP
- What OOP Doesn’t Mean
- What is an object?
- We’ve lost the plot.
-
Object Composition
- What is Object Composition?
- Three Different Forms of Object Composition
- Notes on Code Examples
- Aggregation
- Concatenation
- Delegation
- Conclusion
-
Factory Functions
- Literals for One, Factories for Many
- Returning Objects
- Destructuring
- Computed Property Keys
- Default Parameters
- Type Inference
- Factory Functions for Mixin Composition
- Conclusion
-
Functional Mixins
- Motivation
- What are mixins?
- What is functional inheritance?
- What is a functional mixin?
- Composing Functional Mixins
- When to Use Functional Mixins
- Caveats
- Conclusion
-
Why Composition is Harder with Classes
- The Delegate Prototype
-
The
.constructorProperty - Class to Factory is a Breaking Change
-
Composable Custom Data Types
- You can do this with any data type
- Composable Currency
-
Lenses
- Why Lenses?
- Background
- Lens Laws
- Composing Lenses
-
Transducers
- Why Transducers?
- Background and Etymology
- A Musical Analogy for Transducers
- Transducers compose top-to-bottom.
- Transducer Rules
- Transducing
- The Transducer Protocol
- Conclusion
-
Elements of JavaScript Style
- 1. Make the function the unit of composition. One job for each function.
- 2. Omit needless code.
- 3. Use active voice.
- 4. Avoid a succession of loose statements.
- 5. Keep related code together.
- 6. Put statements and expressions in positive form.
- 7. Use parallel code for parallel concepts.
- Conclusion: Code should be simple, not simplistic.
-
Mocking is a Code Smell
- TDD should lead to better design.
- What is a code smell?
- What is a mock?
- What is a unit test?
- What is test coverage?
- What is tight coupling?
- What causes tight coupling?
- What does composition have to do with mocking?
- How do we remove coupling?
- “Code smells” are warning signs, not laws. Mocks are not evil.
The Leanpub 45-day 100% Happiness Guarantee
Within 45 days of purchase you can get a 100% refund on any Leanpub purchase, in two clicks.
See full terms
Do Well. Do Good.
Authors have earned$10,815,594writing, publishing and selling on Leanpub, earning 80% royalties while saving up to 25 million pounds of CO2 and up to 46,000 trees.
Learn more about writing on Leanpub
Free Updates. DRM Free.
If you buy a Leanpub book, you get free updates for as long as the author updates the book! Many authors use Leanpub to publish their books in-progress, while they are writing them. All readers get free updates, regardless of when they bought the book or how much they paid (including free).
Most Leanpub books are available in PDF (for computers), EPUB (for phones and tablets) and MOBI (for Kindle). The formats that a book includes are shown at the top right corner of this page.
Finally, Leanpub books don't have any DRM copy-protection nonsense, so you can easily read them on any supported device.
Learn more about Leanpub's ebook formats and where to read them
Top Books
- #1
Aprendiendo Git
Miguel Angel Durán GarcíaGit no es complicado... ¡Si lo entiendes! 😜
¿Sientes que sabes usarlo porque has memorizado todos los comandos que necesitas? ¡Pero no entiendes qué hace cada cosa y por qué! Así es normal que, cuando exista un problema, te cueste resolverlo.
¡Con este libro vas a entender de una vez por todas todo lo que es Git y cómo sacarle provecho!
- #2
Windows Kernel Programming, Second Edition
Pavel Yosifovich - #3
Windows 10 System Programming, Part 2
Pavel Yosifovich - #4
Ansible for DevOps
Jeff GeerlingAnsible is a simple, but powerful, server and configuration management tool. Learn to use Ansible effectively, whether you manage one server—or thousands.
- #5
Functional Programming Made Easier
Charles ScalfaniA Functional Programming book from beginner to advanced without skipping a single step along the way.
In my 40 years of programming, I've felt that programming books always let me down, especially Functional Programming books. So, I wrote the book I wish I had 5 years ago.
Functional Programming will never be easy, but it can be easier.
- #6
C++20
Rainer GrimmC++20 is the next big C++ standard after C++11. As C++11 did it, C++20 changes the way we program modern C++. This change is, in particular, due to the big four of C++20: ranges, coroutines, concepts, and modules.
- #7
Agile Testing Condensed Thai Edition
Janet Gregory, Suthasinee Lieopairoj, Sahassa Intarit, and Prathan Dansakulcharoenkitหนังสือ Agile Testing Condensed นำเสนอภาพรวมที่กระชับ อ่านง่าย เกี่ยวกับวิธีการประสบความสำเร็จในการทดสอบซอฟต์แวร์ และสร้างวัฒนธรรมที่มุ่งเน้นการส่งมอบซอฟต์แวร์ที่มีคุณภาพในบริบทของการพัฒนา ตรวจสอบ ทดสอบ เพื่อส่งมอบผลลัพธ์จากซอฟต์แวร์ในรูปแบบของแอจไจล์ จากองค์ความรู้ และประสบการณ์กว่ายี่สิบปีของ Janet Gregory และ Lisa Crispin
- #8
Jetpack Compose internals
Jorge CastilloJetpack Compose is the future of Android UI. Master how it works internally and become a more efficient developer with it. You'll also find it valuable if you are not an Android dev. This book provides all the details to understand how the Compose compiler & runtime work, and how to create a client library using them.
- #9
Introducing EventStorming
Alberto BrandoliniThe deepest tutorial and explanation about EventStorming, straight from the inventor.
- #10
OpenIntro Statistics
David Diez, Christopher Barr, Mine Cetinkaya-Rundel, and OpenIntroA complete foundation for Statistics, also serving as a foundation for Data Science.
Leanpub revenue supports OpenIntro (US-based nonprofit) so we can provide free desk copies to teachers interested in using OpenIntro Statistics in the classroom and expand the project to support free textbooks in other subjects.
More resources: openintro.org.
Top Bundles
- #1
Software Architecture for Developers: Volumes 1 & 2 - Technical leadership and communication
2 Books
"Software Architecture for Developers" is a practical and pragmatic guide to modern, lightweight software architecture, specifically aimed at developers. You'll learn:The essence of software architecture.Why the software architecture role should include coding, coaching and collaboration.The things that you really need to think about before... - #2
CCIE Service Provider Ultimate Study Bundle
2 Books
Piotr Jablonski, Lukasz Bromirski, and Nick Russo have joined forces to deliver the only CCIE Service Provider training resource you'll ever need. This bundle contains a detailed and challenging collection of workbook labs, plus an extensively detailed technical reference guide. All of us have earned the CCIE Service Provider certification... - #3
Modern C++ Collection
3 Books
Get All about Modern C++C++ Standard Library, including C++20Concurrency with Modern C++, including C++20C++20Each book has about 200 complete code examples. Updates are included. When I update one of the books, you immediately get the updated bundle. You can expect significant updates to each new C++ standard (C++23, C++26, .. ) and also... - #4
The Python Craftsman
3 Books
The Python Craftsman series comprises The Python Apprentice, The Python Journeyman, and The Python Master. The first book is primarily suitable for for programmers with some experience of programming in another language. If you don't have any experience with programming this book may be a bit daunting. You'll be learning not just a programming... - #6
10 Books Bundle - A New Career in Tech 🚀
10 Books
Do you want to create yourself a new and profitable skillset - in one year or less? Do you want to position yourself on the right side of change finally? Do you want to work from home and set your own work schedule while choosing fun and interesting coding projects? Software developers and freelance developersearn six figuresin the US, according... - #8
Pattern-Oriented Memory Forensics and Malware Detection
2 Books
This training bundle for security engineers and researchers, malware and memory forensics analysts includes two accelerated training courses for Windows memory dump analysis using WinDbg. It is also useful for technical support and escalation engineers who analyze memory dumps from complex software environments and need to check for possible...
