Showcase of the observer design pattern

Observer Pattern

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

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();