Asynchronous JavaScript Skill

Quick Reference Card

Event Loop Order

1. Call Stack (sync code)
2. Microtasks (Promise.then, queueMicrotask)
3. Macrotasks (setTimeout, setInterval, I/O)

console.log('1');                    // Sync
setTimeout(() => console.log('2'), 0);  // Macro
Promise.resolve().then(() => console.log('3')); // Micro
console.log('4');                    // Sync
// Output: 1, 4, 3, 2