Observer in JavaScript

observer_example.js

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);
  }
};

// Turning them into publishers
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();

console.log('.... removing a subscriber');
blogger.removeSubscriber(jill.gossip);
blogger.writeBlogPost();

console.log('... try the la_times publisher');
la_times.addSubscriber(jill.gossip);
la_times.newIssue();