FlatMap

flatmap.ts

var source = Rx.Observable
    .range(1, 2)
    .flatMap(function (x) {
        return Rx.Observable.range(x, 2);
    });

var subscription = source.subscribe(
    function (x) { console.log('Next: ' + x); },
    function (err) { console.log('Error: ' + err); },
    function () { console.log('Completed'); });

// Next: 1, 2, 2, 3
// when 1 from outer observable is passed in it results into 1, 2
// when 2 from outer observable is passed in it results into 2, 3
// All the results matter here from the source unlike switchMap.