Event Loop Revision Checklist

Core idea

JavaScript handles async work by coordinating the call stack, task queues, and microtask queues.

Revision points

• Promise.then callbacks run in the microtask queue.
• setTimeout callbacks enter the task queue.
• The browser or runtime drains microtasks before moving to the next task.

console.log("start");

setTimeout(() => console.log("timeout"), 0);
Promise.resolve().then(() => console.log("promise"));

console.log("end");

Expected order: start, end, promise, timeout.