I have three promises, Rest requests returning lists of data.

The third one has references (ids) to the first two lists, so I want to map these ids to corresponding names when I have all the data.

The mapping isn't an issue, I just use Lodash for that.

But the issue is to wait for the three promises to resolve before starting to computing this mapping.

I figured out to use concat():

Rx.Observable.concat(p1, p2, p3).subscribe(

function onNext(list)

{

  // Assign the list to the corresponding variable in the scope

},

function onError(e)

{

  // Notify of error

},

function onCompleted()

{

  // Do the mapping

}

);

My problem is that onNext() will be called in random order. Ie. I don't know which list I receive at some point, and it is hard to tell from the data it contains.

Is there a way to track which promises produced which list? A kind of zip? concatMap? concatMapObserver? I admit I haven't fully understood the usage of the last two...