gistfile1.txt

  /*
   * Performs a exclusive waiting for the first to finish before subscribing to another observable.
   * Observables that come in between subscriptions will be dropped on the floor.
   * @returns {Observable} A exclusive observable with only the results that happen when subscribed.
   */
  observableProto.exclusive = function () {
    var sources = this;
    return new AnonymousObservable(function (observer) {
      var hasCurrent = false,
        isStopped = true,
        m = new SingleAssignmentDisposable(),
        g = new CompositeDisposable();

      if (!hasCurrent) {
        hasCurrent = true;
        g.add(m);

        m.setDisposable(sources.subscribe(
          function (innerSource) {

            isPromise(innerSource) && (innerSource = observableFromPromise(innerSource));

            var innerSubscription = new SingleAssignmentDisposable();
            g.add(innerSubscription);

            innerSubscription.setDisposable(innerSource.subscribe(
              observer.onNext.bind(observer),
              observer.onError.bind(onError),
              function () {
                g.remove(innerSubscription);
                if (isStopped && !hasCurrent && g.length === 1) {
                  observer.onCompleted();
                }
            ));
        },
        observer.onError.bind(observer),
        function () {
          hasCurrent = false;
          isStopped = true;
          if (g.length === 1) { 
            observer.onCompleted();
          }
        }));
      }

      return g;
    });
  };