You Don't Know JS Yet: Scope & Closures
You Don't Know JS Yet: Scope & Closures
About the Book
The worldwide best selling You Don't Know JS book series is back for a 2nd edition: You Don't Know JS Yet. All 6 books are brand new, rewritten to cover all sides of JS for 2020 and beyond. You'll still get in-depth coverage of the core language, applied in useful code organization patterns for your programs. And of course, through Kyle's unique perspective and conversational tone, explore passionate, reasoned debate of the most common questions developers face.
Scope & Closures, the second book in the new edition series, dives deep into how and why to organize variables into different buckets of scope, limiting scope over-exposure and improving code maintainability. On top of lexical scope, closure empowers functions with memory, preserving variables across calls. Modules leverage scope and closures to encapsulate data and behavior.
In Scope & Closures, you'll dig into:
- Nesting lexical scopes with functions and blocks, to limit scope exposure of variables
- Functions remembering variables through closure
- Modules, one of the most important code organization patterns in programming
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Table of Contents
- The Parts
- The Title?
- The Mission
- The Path
Chapter 1: What’s the Scope?
- About This Book
- Compiled vs. Interpreted
- Compiling Code
- Compiler Speak
- Cheating: Runtime Scope Modifications
- Lexical Scope
Chapter 2: Illustrating Lexical Scope
- Marbles, and Buckets, and Bubbles… Oh My!
- A Conversation Among Friends
- Nested Scope
- Continue the Conversation
Chapter 3: The Scope Chain
- “Lookup” Is (Mostly) Conceptual
- Function Name Scope
- Arrow Functions
- Backing Out
Chapter 4: Around the Global Scope
- Why Global Scope?
- Where Exactly is this Global Scope?
- Global This
- Globally Aware
Chapter 5: The (Not So) Secret Lifecycle of Variables
- When Can I Use a Variable?
- Hoisting: Yet Another Metaphor
- Uninitialized Variables (aka, TDZ)
- Finally Initialized
Chapter 6: Limiting Scope Exposure
- Least Exposure
- Hiding in Plain (Function) Scope
- Scoping with Blocks
- Function Declarations in Blocks (FiB)
- Blocked Over
Chapter 7: Using Closures
- See the Closure
- The Closure Lifecycle and Garbage Collection (GC)
- An Alternative Perspective
- Why Closure?
- Closer to Closure
Chapter 8: The Module Pattern
- Encapsulation and Least Exposure (POLE)
- What Is a Module?
- Node CommonJS Modules
- Modern ES Modules (ESM)
- Exit Scope
Appendix A: Exploring Further
- Implied Scopes
- Anonymous vs. Named Functions
- Hoisting: Functions and Variables
The Case for
- What’s the Deal with TDZ?
- Are Synchronous Callbacks Still Closures?
- Classic Module Variations
Appendix B: Practice
- Buckets of Marbles
- Closure (PART 1)
- Closure (PART 2)
- Closure (PART 3)
- Suggested Solutions
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