import { interval } from 'rxjs';
import { take, finalize } from 'rxjs/operators';
​
//emit value in sequence every 1 second
const source = interval(1000);
//output: 0,1,2,3,4,5....
const example = source.pipe(
  take(5), //take only the first 5 values
  finalize(() => console.log('Sequence complete')) // Execute when the observable completes
)
const subscribe = example.subscribe(val => console.log(val));