Observer Pattern

gistfile1.txt

var Subject = function() {
  var observers = [];

  return {


    subscribeObserver: function(observer) {
      observers.push(observer);
    },
    unsubscribeObserver: function(observer) {
      var index = observers.indexOf(observer);
      if(index > -1) {
        observers.splice(index, 1);
      }
    },
    notifyObserver: function(observer) {
      var index = observers.indexOf(observer);
      if(index > -1) {
        observers[index].notify(index);
      }
    },
    notifyAllObservers: function() {
      for(var i = 0; i < observers.length; i++) {
        observers[i].notify(i);
      }
    }
  }
};

var Observer = function() {
  return {
    notify: function(index) {
      console.log("Observer " + index + " is notified!");
    }
  }
}

var subject = new Subject();

var observer1 = new Observer();
var observer2 = new Observer();
var observer3 = new Observer();
var observer4 = new Observer();

subject.subscribeObserver(observer1);
subject.subscribeObserver(observer2);
subject.subscribeObserver(observer3);
subject.subscribeObserver(observer4);

subject.notifyObserver(observer2);

subject.notifyAllObservers();