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$10,623,269writing, 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
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.
- #2
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.
- #3
Stratospheric
Tom Hombergs, Björn Wilmsmann, and Philip RiecksFrom Zero to Production with Spring Boot and AWS. All you need to know to get a Spring Boot application into production with AWS. No previous AWS knowledge required.
- #4
Thinking with Types
Sandy MaguireThis book aims to be the comprehensive manual for type-level programming. It's about getting you from here to there---from a competent Haskell programmer to one who convinces the compiler to do their work for them.
- #5
A Practical Guide to Testing in DevOps Japanese Edition
Katrina Clokie, Yuya Kazama, and Masanori KawaradaKatrina Clokieによる2017年8月発行の書籍『A Practical Guide to Testing in DevOps』の日本語翻訳版です。実装前や実装中でのテストだけでなく、本番環境でのテストについて、数多くの事例を用いて語られています。
- #6
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.
- #7
Continuous Delivery Pipelines
Dave FarleyThis practical handbook provides a step-by-step guide for you to get the best continuous delivery pipeline for your software.
- #8
Practical FP in Scala: A hands-on approach
Gabriel VolpeA practical book aimed for those familiar with functional programming in Scala who are yet not confident about architecting an application from scratch.
Together, we will develop a purely functional application using the best libraries in the Cats ecosystem, while learning about design patterns and best practices.
- #9
Algebra-Driven Design
Sandy MaguireA how-to field guide on building leak-free abstractions and algebraically designing real-world applications.
- #10
The Python Journeyman
Robert Smallshire, Austin Bingham, and Sixty NorthOne of Python's strengths is that it's approachable and easy to learn, so that almost anyone can learn to write a basic Python program. The Python Journeyman will take you beyond that, beyond the basics. We will lead you through some of the deeper aspects of Python, and give you the skills you need to write great Python programs.
Top Bundles
- #1
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... - #2
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... - #4
Retromat eBook Bundle for Agile Retrospectives
2 Books
If you facilitate retrospectives this bundle is for you: "Plans for Retrospectives" helps beginners learn the lay of the land with tried-and-true plans. Once you know your way around, "Run great agile retrospectives" contains all 135+ activities in Retromat for you to mix and match. - #6
9 Books-Bundle: Shut Up and Code!
9 Books
"Shut up and code." Laughter in the audience. The hacker had just plugged in his notebook and started sharing his screen to present his super-smart Python script. "Shut up and code" The letters written in a white literal coding font on black background was the hackers' home screen background mantra. At the time, I was a first-year computer... - #8
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...
