I'm having trouble figuring out what's wrong with my code. The issue pertains to the observer pattern in JavaScript. I keep getting an error that says "Uncaught TypeError: Cannot read property 'push' of undefined". My guess is that this error occurs because the "observers" key is not being created on the object when I use the new keyword.
Js Fiddle: https://jsfiddle.net/2808w5x0/
function Subject(){
this.observers = [];
return {
subscribeObserver:function(observer){
observers.push(observer);
},
getObservers:function(){return this.observers;},
unSubscribeObserver:function(observer){
var index = this.observers.indexof(observer);
if(index > -1){
this.observers.splice(index,1);
}
},
notifyObserver:function(observer){
var index = this.observers.indexof(observer);
if(index > -1){
this.observer[index].notify(index);
}
},
notifyAllObserver:function(){
this.observers.foreach(function(val,idx){
val.notify(idx);
});
}
};
}
function Observer(){
return{
notify:function(idx){
console.log("Observer " + idx + " notified.");
}
}
}
var subject = new Subject();
console.log("subject ",subject.getObservers());
var ob1 = new Observer();
var ob2 = new Observer();
var ob3 = new Observer();
var ob4 = new Observer();
subject.subscribeObserver(ob1);
subject.subscribeObserver(ob2);
subject.subscribeObserver(ob3);
subject.subscribeObserver(ob4);
subject.notifyAllObserver();