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

Table of Contents

1. Thank You
2. Composing Software: An Introduction
3. The Dao of Immutability (The Way of the Functional Programmer)
4. The Rise and Fall and Rise of Functional Programming (Composable Software)
5. Why Learn Functional Programming in JavaScript?
6. Pure Functions
7. What is Functional Programming?
8. A Functional Programmer's Introduction to JavaScript
9. Higher Order Functions
10. Curry and Function Composition
11. Abstraction & Composition
12. Abstract Data Types and the Software Crisis
13. Functors & Categories
14. Monads
15. The Forgotten History of OOP
16. Object Composition
17. Factory Functions
18. Functional Mixins
19. Why Composition is Harder with Classes
20. Composable Custom Data Types
21. Lenses
22. Transducers
23. Elements of JavaScript Style
24. Mocking is a Code Smell

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 top tech companies.