<html><head><script type="text/javascript">
function Subject () {
this.observers = new Array();
this.register_observer = function(observer){
this.observers.push(observer);
}
this.remove_observer = function(observer){
for(var i=0; i < this.observers.length; i++){
if(this.observers[i] === observer){
this.observers.splice(i, 1);
}
}
}
this.set_value = function(value){
this.value = value
this.inform_observers()
}
this.inform_observers = function(){
for each (var observer in this.observers){
observer.update(this.value)
}
}
}
function Observer1 (subject){
subject.register_observer(this);
this.update = function(value){
document.write("I'm observer 1 and subject value is "+value+"<br>\n");
}
}
function Observer2 (subject){
subject.register_observer(this);
this.update = function(value){
document.write("I'm observer 2 and subject value is "+value+"<br>\n");
}
}
</script>
</head>
<body>
<script type="text/javascript">
var subject = new Subject();
var observer1 = new Observer1(subject);
var observer2 = new Observer2(subject);
subject.set_value(1);
subject.remove_observer(observer1);
subject.set_value(3);
</script></body></html>
