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<!doctype html>
<html lang="en">
<head>
<title>JavaScript Patterns</title>
<meta charset="utf-8">
</head>
<body>
<script>
/* Title: Observer
Description: is a publish/subscribe pattern which allows a number of observer objects to see an event
*/
var observer = {
addSubscriber:function (callback) {
this.subscribers[this.subscribers.length] = callback;
},
removeSubscriber:function (callback) {
for (var i = 0; i < this.subscribers.length; i++) {
if (this.subscribers[i] === callback) {
delete(this.subscribers[i]);
}
}
},
publish:function (what) {
for (var i = 0; i < this.subscribers.length; i++) {
if (typeof this.subscribers[i] === 'function') {
this.subscribers[i](what);
}
}
},
make:function (o) { // turns an object into a publisher
for (var i in this) {
o[i] = this[i];
o.subscribers = [];
}
}
};
var blogger = {
writeBlogPost:function () {
var content = 'Today is ' + new Date();
this.publish(content);
}
};
var la_times = {
newIssue:function () {
var paper = 'Martians have landed on Earth!';
this.publish(paper);
}
};
observer.make(blogger);
observer.make(la_times);
var jack = {
read:function (what) {
console.log('I just read that ' + what)
}
};
var jill = {
gossip:function (what) {
console.log('You didn\'t hear it from me, but ' + what)
}
};
blogger.addSubscriber(jack.read);
blogger.addSubscriber(jill.gossip);
blogger.writeBlogPost();
blogger.removeSubscriber(jill.gossip);
blogger.writeBlogPost();
la_times.addSubscriber(jill.gossip);
la_times.newIssue();
// reference
// http://www.addyosmani.com/resources/essentialjsdesignpatterns/book/#observerpatternjavascript
// http://shop.oreilly.com/product/9780596806767.do?sortby=publicationDate
</script>
</body>
</html>