Combining input streams then using scan to track the results is a common scenario when coding with streams. This lesson walks you through setting up two buttons and merging their input events together to build a streaming Counter component.
const CounterStream = componentFromStream( props$ => { const { stream: onInc$, handler: onInc } = createEventHandler(); const { stream: onDec$, handler: onDec } = createEventHandler(); return props$ .switchMap( propos => Observable.merge( onInc$.mapTo(1), onDec$.mapTo(-1) ) .startWith(propos.value) .scan((acc, curr) => acc + curr) .map((value) => ({ value, onInc, onDec }))) .map( Counter ) } );
