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JavaScript75 min total · 15 parts

JavaScript Core Concepts: Scope, Closures, `this`, and the Event Loop

Contents — Part 1 of 15: Overview
  1. 1.Overview
  2. 2.Scope: Global, Function, and Block
  3. 3.var vs. let vs. const: A Direct Comparison
  4. 4.Hoisting and the Temporal Dead Zone
  5. 5.Closures: A Function Remembers Where It Was Created
  6. 6.Practical Closure Patterns: Memoization, Debounce, and the Module Pattern
  7. 7.this: How It Gets Bound
  8. 8.The Call Stack and Stack Overflows
  9. 9.Synchronous vs. Asynchronous Execution
  10. 10.Promises: Representing a Future Value
  11. 11.async/await: Promises With Synchronous-Looking Syntax
  12. 12.The Event Loop: Microtasks vs. Macrotasks
  13. 13.Where Rendering Fits In
  14. 14.setTimeout, setInterval, and Their Gotchas
  15. 15.Common Mistakes Worth Remembering
Part 1 of 15 · ~1 min

Overview

Most confusing JavaScript behavior traces back to a small set of mechanisms: how scope and hoisting work, what a closure actually captures, how this gets bound, how the call stack unwinds, and how the event loop orders asynchronous code. This is a complete reference for all of them together, since they constantly interact in real code — work through it in order, or jump straight to the section you need from the sidebar.

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Scope: Global, Function, and Block