What is the difference between Promises and Observables?

#rxjs

Both observables and promises help us work with asynchronous functionality in JavaScript. Promises deal with one asynchronous event at a time, while observables handle a sequence of asynchronous events over a period of time.

Here are the differences in concept between Observables and Promises.

Observables	Promises
Emit multiple values over a period of time.	Emit a single value at a time.
Are lazy: they’re not executed until we subscribe to them using the subscribe() method.	Are not lazy: execute immediately after creation.
Have subscriptions that are cancellable using the unsubscribe() method, which stops the listener from receiving further values.	Are not cancellable.
Provide the map, filter, reduce, retry, retryWhen, and so many other RxJS operators, that makes it easy to deal with Observables.	Don’t provide any operations.
Deliver errors to the subscribers.	Push errors to the child promises.