Before Promises, JavaScript relied on callback functions for async operations, leading to the infamous callback hell. Promises introduced a cleaner way to handle asynchronous code, and async/await made it even more readable.
A Promise represents a value that may not be available yet. It can be pending, fulfilled, or rejected. You chain .then() and .catch() handlers to react to completion or failure.
Async/await is syntactic sugar over Promises. An async function always returns a Promise, and the await keyword pauses execution until a Promise settles. This makes async code look and behave like synchronous code.
When to use which: Use async/await for most cases — it is cleaner and easier to debug. Reserve raw Promises when you need Promise.all() for parallel execution, or when composing multiple async chains. Avoid mixing callbacks with Promises.
Error handling with async/await uses standard try/catch blocks, making it more intuitive than .catch() chains. However, be careful with parallel async operations — use Promise.all() or Promise.allSettled() instead of sequential awaits when operations are independent.