Rx.Observable.prototype.where = function (obj) {
  var me = this;
  return Rx.Observable.create(function (observer) {
    me.subscribe({
      next: function (v) {
        for (var key in obj) {
          if (v[key] !== obj[key]) {
            return;
          }
        }
          
        observer.next(v);
      },
      error: function (err) { observer.error(err) },
      complete: function () { observer.complete() }
    });
  });
}

var store = {
  message: 1
};

var subject = new Rx.Subject();
subject
  .where({ name: 'increment' })
  .subscribe({
    next: function (e) {
      store.message++;
    }
  });
subject
  .where({ name: 'decrement' })
  .subscribe({
    next: function (e) {
      store.message--;
    }
  });

var app = new Vue({
  el: '#app',
  data: store,
  methods: {
    increment: function () {
      subject.next({ name: 'increment' });
    },
    decrement: function () {
      subject.next({ name: 'decrement' });
    }
  }
});