I have this little peace of code:
var s2 = of(6, 16, 26).pipe(map(v1=>of(5, 15, 25).pipe(map(v2=>[v2,v1]))), combineLatestAll());
s2.subscribe(console.log)
It produces output below - I understand the third output generated (by the time the first stream starts the second one is finished - so it always starts with 25 I guess) but I don't understand why the first two outputs are generated.
[25, 6]
[25, 16]
[5, 26]
[25, 6]
[25, 16]
[15, 26]
[25, 6]
[25, 16]
[25, 26]
This is a timeline of what happens:
O1 [5,6] [15,6] [25,6]
O2 [5,16] [15,16] [25,16]
O3 [5,26] [15,26] [25,26]
CLA latest O1 -> [25,6] [25,6] [25,6]
latest O2 -> [25,16] [25,16] [25,16]
latest O3 -> [5,26] [15,26] [25,26]
combineLatestAll subscribes to all observables. When you subscribe to a stream such as of(5, 15, 25) it completes before anything else can happen. So observable 1 completes, observable 2 completes and the values emitted by observable 3 are each combined with the latest values from O1 and O2.