import { mergeMap, tap, map } from 'rxjs/operators';
import { Observable } from 'rxjs';

this.budgetService.getBudgetDays(this.startDate, this.finishDate)
        .subscribe({
          next(budgetDates) {

          },
          error(error) {
            // not sure but I don't think rxjs should have nested callbacks like this.
            self.budgetTestService.getBudgetDates(self.startDate, self.finishDate)

            .subscribe({
              next(budgetDates) {
              },
              error(error) {}
            });
          }
        });