exhaustMap

RxJS 5 exhaustMap

by Brian Troncone

HTML

<script src="https://npmcdn.com/@reactivex/rxjs@5.0.0-beta.8/dist/global/Rx.umd.js"></script>

JavaScript

const interval = Rx.Observable.interval(1000);
const delayedInterval = interval.delay(10).take(4);

const exhaustSub = Rx.Observable
	.merge(
  	// delay 10ms, then start interval emitting 4 values
		delayedInterval,
    // emit immediately
		Rx.Observable.of(true)
  )
  /*
   *	The first emitted value (of(true)) will be mapped 
   *  to an interval observable emitting 1 value every 
   *  second, completing after 5.
   *  Because the emissions from the delayed interval 
   *  fall while this observable is still active they will be ignored.
   *
   *  Contrast this with concatMap which would queue, 
   *  switchMap which would switch to a new inner observable each emission,
   *  and mergeMap which would maintain a new subscription for each emitted value.
   */
  .exhaustMap(_ => interval.take(5))
  // output: 0, 1, 2, 3, 4
  .subscribe(val => console.log(val))