Asynchronous JavaScript Explained: Callbacks to Async/Await
Updated on December 10, 2025 9 minutes read
Frequently Asked Questions
What is asynchronous JavaScript in simple terms?
Asynchronous JavaScript is code that can start a task, let other work continue, and then handle the result later when the task finishes. It keeps your app responsive while slow operations such as network calls or file access are running.
Should I learn callbacks, promises, async, or await first?
Start by understanding callbacks, because they are the foundation many libraries still use. Then learn promises and async or await, which are the most common patterns in modern JavaScript, and are easier to reason about for complex flows.
Do async or await replace promises?
No. Async or await is syntax that sits on top of promises. Async functions always return promises under the hood, so learning how promises work will help you understand what async or await is really doing.