title: how to return my own observable depending on multiple subscribe of data
body: <p>Struggled for hours and hours..... How can I return an custom observable which depends on multiple chained subscribe on other observables. Like, I call a function and subscribe and check the value of the observable, then decide which other function to call. Then call another http request to get a new observable from the request. Finally, return my custom observable depending on the previous observable.</p>