Right way to handle a Future that returns an either?

[spiffytech]

I'm calling f = Future.fromPromise(p) on a promise containing an Either. I'd like to do f.map (or something like that) on the result and operate on the right value of the Either, possibly returning another future. I can't find a built-in function that does this, so I'm resorting to f.flatMap((e) => Future.of(() => fn(e))).

Is there a better way to do this?