function create(subscriber) {

    var observable = {

        subscribe: function(observer) {

            subscriber(observer)

        }       

    };

    return observable;

}

​

var observable = create(function(observer) {

  observer.next(1);

  observer.next(2);

  observer.next(3);

})

​

var observer = {

  next: function(value) {

    console.log(value)

  }

}

​

observable.subscribe(observer)