Observable vs Promise | Which is better?
Observable vs Promise | When to use Promise
Observable vs Promise | When to use Observable
Key Takeaways
- Use async/await for more readable and manageable asynchronous code.
- Promises are suitable for handling single events without relying on third-party libraries.
- Unlike Promises, Observables can emit multiple values and can be cancelled.
- Use Promises when you don't need to cancel the async operation.
When you want to use async/await
Async/await is excellent for simplifying your Promise-based code. Recent advances in JavaScript, as of 2026, have made async/await the go-to choice for most developers dealing with asynchronous programming. It literally transforms your complex Promise chains into more straightforward, linear code. So, whenever you feel like your async flow looks convoluted, async/await can make it much easier to read and maintain.
When you don't want to rely on third-party libraries
Promises remain a core feature of JavaScript and don't require any additional dependencies like RxJS. This is particularly useful if you aim to minimize external libraries in your JavaScript projects. Modern browsers continue to support Promises natively, making them a reliable choice for anyone seeking to keep their tech stack minimal.
When you want to resolve a single event
Promises are perfect for scenarios where you need to handle a single asynchronous event. Unlike Observables, which can emit a series of values over time, Promises are one-shot deals. They either resolve or reject once, and that's it. This makes them ideal for actions like HTTP requests or file operations where you only expect one successful result or one failure.
When you don't want to cancel an async activity
One downside of Promises is their inability to be canceled. Once you've kicked off a Promise, it will run to completion regardless of whether you still need the result or not. If your use case doesn't require cancellation, Promises are straightforward and effective. For cancellable operations, you'd want to consider using Observables instead.
FAQ
Why would I use Promises over Observables?
Promises are straightforward and ideal for single-value asynchronous events. They make your code easier to reason about when combined with async/await, and don’t require additional libraries.
What if I need to handle multiple events over time?
If you need to process a stream of data or events, like handling user input or WebSocket messages, Observables are better suited as they can emit multiple values over time.
Can I cancel an async operation initiated by a Promise?
No, Promises can't be canceled. They will complete once started. If cancellation is necessary, consider using Observables or other approaches that provide cancellation mechanisms.
