JavaScript Engine Internals

Deep-dive into how the JavaScript engine actually runs your code — from the event loop and call stack to closures, prototypes, and memory management.

Event Loop

Call Stack

Microtask Queue

Web APIs

Promises

Async/Await

Closures

Scope Chain

this

Prototypes

Modules

GC (V8)

Memory Leaks

Core Runtime

How JavaScript handles async operations with a single thread — task queue, microtask queue, and the render cycle.

How setTimeout, fetch, requestAnimationFrame, and other Web APIs integrate with the JS engine.

Async Model

Promise resolution, microtask queue priority, and how .then() chains schedule work.

How the compiler transforms async functions into generator-based state machines.

Scope & OOP

How lexical scoping works, closure memory model, and variable capture.

4 binding rules — default, implicit, explicit, new — plus arrow function lexical this.

The prototype chain, __proto__ vs prototype, and how ES6 classes map to prototypes.

Memory & Modules

Mark-and-sweep, generational GC, Scavenger vs Mark-Compact, and memory profiling.

Static vs dynamic imports, tree-shaking, circular dependencies, and dual packages.

Detached DOM nodes, closures over large scopes, WeakRef, and Chrome DevTools heap snapshots.