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SolomonSScott/example-observer-pattern.js

Last active May 22, 2016 18:47
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example-observer-pattern.js
var Subject = function() {
this.observers = [];
return {
subscribeObserver: function(observer) {
this.observers.push(observer);
},
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.observers[index].notify(index);
}
},
notifyAllObservers: function() {
for(var i = 0; i < this.observers.length; i++){
this.observers[i].notify(i);
};
}
};
};
var Observer = function() {
return {
notify: function(index) {
console.log("Observer " + index + " is notified!");
}
}
}
// Create new subject instance
var subject = new Subject();
// Create different observers
var observer1 = new Observer();
var observer2 = new Observer();
var observer3 = new Observer();
var observer4 = new Observer();
// Subscibe observers to subjects/event
subject.subscribeObserver(observer1);
subject.subscribeObserver(observer2);
subject.subscribeObserver(observer3);
subject.subscribeObserver(observer4);
// Call event
subject.notifyObserver(observer2); // Observer 2 is notified!
subject.notifyAllObservers();
// Observer 1 is notified!
// Observer 2 is notified!
// Observer 3 is notified!
// Observer 4 is notified!
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