switchmap-example.js

const { interval, Observable } = Rx;
const { map, take, switchMap, startWith } = RxOperators;

// Emit value 1 at 1 second
// Emit value 3 at 4 seconds
// Emit value 5 at 5.5 seconds
// Complete at 5.5 seconds
function outerObservable() {
  return new Observable(subscriber => {
    setTimeout(() => {
    	subscriber.next(1);
    }, 1000);
    
    setTimeout(() => {
    	subscriber.next(3);
    }, 4000);
    
    setTimeout(() => {
    	subscriber.next(5);
      subscriber.complete();
    }, 5500);
  }) 
}

// Emit the value 10 every second, starting at time 0, for 3 total seconds
function innerObservable() {
  const valuesToEmit = [10, 10];
  return interval(1000).pipe(
    take(valuesToEmit.length),
    map(index => valuesToEmit[index]),
    startWith(10) // emits 10 at time zero
  )
}

outerObservable().pipe(
  switchMap(outerObservableValue => {
    return innerObservable().pipe(
      map(innerObservableValue => {
        return innerObservableValue * outerObservableValue;
      })
    );
  })
);