What are the similarities and differences between Observable and Promise?

Similarities:

• Represent asynchronous operations.
• Use functions to handle the result (resolved) and error (rejected).

Differences:

Feature	Promise	Observable
Value/Event	Returns a single value or error.	Returns 0 or more values over time.
Cancellation	Cannot be canceled after starting.	Can cancel subscription.
Multiple subscribers	Single execution regardless of subscribers.	New unsubscription usually leads to new execution (cold Observable).
Laziness	Starts executing immediately after creation.	Starts executing only after subscription.
Operators	No built-in operators for transformation.	Has a rich set of operators (map, filter, merge, etc.).
Use cases	HTTP requests, deferred actions.	UI events, WebSocket connections, intervals.

Example of Observable:

import { Observable } from 'rxjs';

const observable = new Observable(subscriber => {
  subscriber.next(1);
  subscriber.next(2);
  setTimeout(() => {
    subscriber.next(3);
    subscriber.complete();
  }, 1000);
});

Example of Promise:

const promise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('Data received');
  }, 1000);
});