You Don’t Know JS Yet
Master JavaScript by understanding how it really works
A deep dive into the core mechanisms of JavaScript—from scope and closures to prototypes, types, and beyond. Written by Kyle Simpson.
Start Your Journey
Begin your exploration of JavaScript’s fundamental concepts.Get Started
Build a solid foundation in JavaScript fundamentals
Read the Preface
Understand the philosophy behind this book series
The Books
Master JavaScript’s three foundational pillars through comprehensive exploration.Get Started
What is JavaScript? Survey the language and understand its core principles.
Scope & Closures
Deep dive into lexical scope, hoisting, closure, and the module pattern.
Objects & Classes
Understand prototypes, this keyword, and the class system.
Types & Grammar
Master JavaScript’s type system and coercion mechanisms.
Key Topics
Explore the core mechanisms that power JavaScript.Scope & Closures
Lexical scope, function scope, block scope, and closure patterns
Prototypes
Prototype chain, object delegation, and behavior sharing
Types & Coercion
Primitive values, type conversion, and implicit coercion
this Keyword
Call-site, binding rules, and arrow function behavior
Classes
Class syntax, inheritance, and static methods
Modules
CommonJS, ES Modules, and encapsulation patterns
About the Series
This book series is designed for developers who want to truly understand JavaScript, not just use it. Each book explores a fundamental pillar of the language in depth, challenging you to think beyond “good enough to work” and strive for complete mastery.These books assume you already have 6-9 months of JavaScript experience. They are not beginner introductions, but deep explorations of how JavaScript really works.