The core idea
JavaScript often needs to wait for work that completes later, such as a network request, a timer, or reading a file. Asynchronous code allows other work to continue instead of blocking the entire execution flow.
How it works
A Promise represents the eventual result of an asynchronous operation. It can be pending, fulfilled, or rejected. Promise methods such as then and catch let code respond to those outcomes.
Practical considerations
An async function always returns a Promise. Inside it, await pauses that function until a Promise settles, then returns its fulfilled value or throws its rejection reason.
A useful way to apply it
Use try and catch around awaited operations when you need to handle errors. For network requests, also check response.ok because an HTTP error status does not necessarily reject fetch automatically.
Keep learning
Avoid awaiting independent requests one after another when they can run concurrently. Promise.all can start multiple operations and wait for all of them, while Promise.allSettled reports each outcome.
Frequently asked questions
Does await block JavaScript?
Await pauses the execution of the surrounding async function, but it does not block the browser's main event loop in the same way as synchronous work.
What happens if an awaited Promise rejects?
The rejection is thrown at the await expression and can be handled with try and catch.
When should I use Promise.all?
Use Promise.all when several independent asynchronous operations must all succeed before continuing.
Continue learning
Explore more topics in the MicroProgrammer library, or browse the JavaScript collection for related guides.