// async iteration in JavaScript?

function SelectAsync(asyncGenerator, asyncProjection) {
  return function(cancellationToken) {
    return spawnSequence(function*(Yielder){
      foreach (asyncItem in asyncGenerator(cancellationToken)) {
        var item = yield asyncItem;
        var result = yield asyncProjection(item, cancellationToken);
        yield Yielder.Result(result);
      }
      yield Yielder.Return();
    }
  }
}