Ask ten developers how the JavaScript event loop works, and you'll get eleven different answers. That's because the event loop is invisible. You can't console.log it. You can't set a breakpoint on it. You just have to know it's there, orchestrating everything.
This guide changes that. We'll walk through the event loop step by step, with code you can actually run and see in JS Visualizer — watching functions enter the call stack, callbacks move through Web APIs, and promises flush from the microtask queue.
The Puzzle That Trips Everyone Up
Before we dive in, try to predict the output of this code:
console.log('A');
