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

The count() operator from the rxjs library is used to count the number of emissions from an observable. It returns a new observable that emits only one value which is the total count of emissions from the source observable.

Here's an example of how to use the count() operator in an observable pipeline:

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

const numbers = from([1, 2, 3, 4, 5]);

numbers.pipe(
  count()
)
.subscribe(count => console.log(`Total count: ${count}`));
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In this example, we created an observable numbers that emits the five numbers 1, 2, 3, 4, and 5. We then used the pipe() method to add the count() operator to the observable pipeline. The subscribe() method was used to subscribe to the output observable and log the total count of emissions.

The output of running this example would be:

index.tsx
Total count: 5
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This indicates that the source observable emitted five values, and the count() operator counted them all, emitting a single value of 5.