What are Promises and how do they work in JavaScript?

Question

What are Promises and how do they work in JavaScript?

Answer

A Promise represents a value that may be available now, later, or never.
It has three states: pending, fulfilled, and rejected.

const promise = new Promise((resolve, reject) => {
  setTimeout(() => resolve('Done!'), 1000);
});

promise.then((result) => console.log(result)); // Done!

They make asynchronous code readable and eliminate callback hell.

Real-World Example

API calls, animations, file I/O, or timers all use Promises under the hood.

Quick Practice

Create a Promise that resolves after 2 seconds and logs “Task completed”.

Summary

Promises simplify async control flow — they’re the foundation of modern async JavaScript.