Observer Pattern example in Javascript

var weatherForcast = { /* observer is a list of subscribers.*/ observers: [], /*weatherChange function will have updated weather*/ weatherChange: function (weather) { for (var i = 0; i < this.observers.length; i++) { this.observers[i].updateUI(weather); } }, /* subscribe function will add a subscriber in observer's list.*/ subscribe: function (widget) { this.observers.push(widget); var self=this; return function(){ self.observers.splice(self.observers.indexOf(widget), 1); }; }, /* Unsubscribe function will remove a subscriber from observer's list.*/ unsubscribe: function(){ this.observers.splice(this.observers.indexOf(Widget), 1) } }; /* Constructor function for Widget(Subscribers).*/ function Widget(name){ this.name = name; } /* function to update all the Subscribers when weather change.*/ Widget.prototype.updateUI = function(weather){ console.log('Weather in ' + this.name + ' is ' + weather + '\xB0C'); }; /* Creating widgets using constructor function*/ var x1 = new Widget('New Delhi'); var x2 = new Widget('Gurgaon'); var x3 = new Widget('Faridabad'); /* Subscribing for weather updates*/ var unsubx1 = weatherForcast.subscribe(x1); var unsubx2 = weatherForcast.subscribe(x2); var unsubx3 = weatherForcast.subscribe(x3); /* weather updated */ weatherForcast.weatherChange(10); console.log('========================'); /* unsubscribing one widget */ unsubx3(); /* weather updated */ weatherForcast.weatherChange(11);