   /**
   *  Runs all observable sequences in parallel and collect their last elements.
   *
   * @example
   *  1 - res = Rx.Observable.forkJoin([obs1, obs2]);
   *  1 - res = Rx.Observable.forkJoin(obs1, obs2, ...);
   * @returns {Observable} An observable sequence with an array collecting the last elements of all the input sequences.
   */
  Observable.forkJoin = function () {
    var allSources = [];
    if (Array.isArray(arguments[0])) {
      allSources = arguments[0];
    } else {
      for(var i = 0, len = arguments.length; i < len; i++) { allSources.push(arguments[i]); }
    }
    return new AnonymousObservable(function (subscriber) {
      var count = allSources.length;
      if (count === 0) {
        subscriber.onCompleted();
        return disposableEmpty;
      }
      var group = new CompositeDisposable(),
        finished = false,
        hasResults = new Array(count),
        hasCompleted = new Array(count),
        results = new Array(count);

      for (var idx = 0; idx < count; idx++) {
        (function (i) {
          var source = allSources[i];
          isPromise(source) && (source = observableFromPromise(source));
          group.add(
            source.subscribe(
              function (value) {
              if (!finished) {
                hasResults[i] = true;
                results[i] = value;
              }
            },
            function (e) {
              finished = true;
              subscriber.onError(e);
              group.dispose();
            },
            function () {
              if (!finished) {
                if (!hasResults[i]) {
                    subscriber.onCompleted();
                    return;
                }
                hasCompleted[i] = true;
                for (var ix = 0; ix < count; ix++) {
                  if (!hasCompleted[ix]) { return; }
                }
                finished = true;
                subscriber.onNext(results);
                subscriber.onCompleted();
              }
            }));
        })(idx);
      }

      return group;
    });
  };
