rx-when example
import { interval } from 'rxjs' import { map, take } from 'rxjs/operators' interval(1000).pipe( take(5), when(v => !(v % 2))( map(v => `${v} is even`), // 'then' operator map(v => `${v} is odd`) // 'else' operator, optional ) ) .subscribe(debug('next:'), debug('error:'), debug('done'))