how to use the finalize function from the rxjs library in javascript

The finalize() operator is used to perform a side effect when an Observable completes or emits an error. Here's an example of how to use finalize() in JavaScript with RxJS:

index.tsx
import { from } from 'rxjs';
import { finalize } from 'rxjs/operators';

const source = from([1, 2, 3]);

const subscription = source.pipe(
  finalize(() => console.log('Observable completed'))
)
.subscribe(console.log); // outputs 1, 2, 3

subscription.unsubscribe(); // logs "Observable completed"
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In this example, the from() operator creates an observable from an array of values. The pipe() operator allows you to chain multiple operators together, in this case, the finalize() operator. When the observable completes or emits an error, finalize() will log a message to the console.

It's important to note that finalize() will always execute, regardless of whether the Observable completes or emits an error.