Event Loop in JavaScript
From the Async JavaScript cheat sheet · Timers & Event Loop · verified Jul 2026
Event Loop
Understand how JavaScript handles asynchronous operations through the event loop mechanism
javascript
// Event loop phases
console.log('1'); // Call stack
setTimeout(() => console.log('2'), 0); // Macrotask queue
Promise.resolve()
.then(() => console.log('3')); // Microtask queue
console.log('4'); // Call stack
// Output: 1, 4, 3, 2💡 JavaScript is single-threaded but uses an event loop for async operations
⚡ Microtasks (promises) have priority over macrotasks (setTimeout)
📌 Understanding the event loop helps debug timing issues
🔄 Call stack must be empty before event loop processes callbacks