From an event map to another event we can use switchMap(), switchMap() accept an function which return an obervable.
The following code: When you click the button, it will start a interval to console out the count...
const Observable = Rx.Observable;
const startButton = document.querySelector('#start');
const start$ = Rx.Observable.fromEvent(startButton, 'click');
const interval$ = Observable.interval(400);
const startInterval$ = start$.switchMap( () => {
return interval$;
});
startInterval$.subscribe( (x) => {
console.log(x);
});
So the start$ switch map to a interval$ to avoid writting the nested subscribe function.
switchMap() actually is pretty useful when dealing with http event stream, it can help to cancel the previous http call.
/*
const startInterval$ = start$.switchMap( () => {
return interval$;
});*/
const startInterval$ = start$.switchMapTo( interval$ );