This book is currently marked as “work in progress” by the author.
You Don’t Know JS Yet: Objects & Classes
Welcome to the third book in the You Don’t Know JS Yet series! This book explores one of JavaScript’s three pillars: the prototype.What This Book Covers
Objects are the most important and varied value type in JavaScript. Every JS program you write will use them in one way or another. This book provides a complete understanding of:- Object Foundations - How objects work as containers for multiple values
- The Prototype Chain - Understanding
[[Prototype]]delegation and inheritance - Classes - Modern
classsyntax and class-oriented design patterns - The
thisKeyword - Mastering dynamic context binding - Delegation - An alternative to class-oriented programming using prototypes
Why Objects Matter
Objects aren’t just containers - they’re the foundation for the prototype system, one of JavaScript’s three core pillars. Prototypes enable JS’s class design pattern and power some of the most widely-used patterns in programming.Chapter 1: Object Foundations
Learn how objects work as containers and master property access, assignment, and manipulation.
Chapter 2: How Objects Work
Dive into property descriptors, the Metaobject Protocol, and the
[[Prototype]] chain.Chapter 3: Classy Objects
Master the
class keyword, inheritance, static members, and private fields.Chapter 4: This Works
Understand how
this binding works and the four rules for this assignment.Chapter 5: Delegation
Explore an alternative design pattern using prototypal delegation instead of classes.
About the Second Edition
This is a complete rewrite of the first edition (titled “this & Object Prototypes”). Since ES6 introduced theclass keyword in 2015, JavaScript has evolved significantly with 7+ yearly updates. This edition reflects JavaScript’s current reality:
- Focus on modern
classsyntax rather than “prototypal classes” - Coverage of ES2015+ features like private fields, static blocks, and more
- New organization starting with objects, building to prototypes, then classes
- Updated for ES2022 and beyond
Prerequisites
Before diving into this book, you should have completed:- Get Started (Book 1) - Foundations of JavaScript
- Scope & Closures (Book 2) - Understanding lexical scope
Start Learning
Begin with Chapter 1
Start your journey into JavaScript objects and classes