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'))