Testing the observers concept in pure JavaScript

EventManagerTest.js

var EventManager = EventManager || {
    handlers: {}
};

EventManager.subscribe = function(event, fn) {
    if (typeof(this.handlers[event]) === 'undefined')
        this.handlers[event] = [];
    this.handlers[event].push(fn);
};

EventManager.unsubscribe = function(event, fn) {
    this.handlers[event] = this.handlers[event].filter(
        function(item) {
            if (item !== fn) {
                return item;
            }
        }
    );
    if (this.handlers[event].length === 0) {
        console.log("Terminating event " + event);
        delete this.handlers[event];
    }
};

EventManager.publish = function(o, thisObj) {
    var scope = thisObj || window;

    if (typeof(this.handlers.book_published) === 'undefined') {
        console.log(o + ' can\'t be published because there are no readers');
        return;
    }

    this.handlers.book_published.forEach(function(item) {
        item.call(scope, o);
    });

};

// ----------------------------------------------

function Reader(name) {
    this.name = name || "Anonymous reader";
    console.log('New reader: ' + this.name);
    var self = this;
    var reaction = function(title) {
        console.log(self.name + ' is reading '+ title);
    };
    this.subscribeToBooks = function() {
        console.log(this.name + ' is subscribing to books');
        EventManager.subscribe('book_published', reaction);
    };
    this.unsubscribeBooks = function() {
        console.log(this.name + ' gave up reading');
        EventManager.unsubscribe('book_published', reaction);
    };
}

var james = new Reader('James');
var harry = new Reader('Harry');
var alice = new Reader('Alice');
james.subscribeToBooks();
EventManager.publish('Lord of the Rings');
harry.subscribeToBooks();
EventManager.publish('World of Narnia');
james.unsubscribeBooks();
EventManager.publish('The Picture of Dorian Grey');
james.subscribeToBooks();
EventManager.publish('The Silmarillion');
james.unsubscribeBooks();
harry.unsubscribeBooks();
EventManager.publish('Alice\'s Adventures in Wonderland');
alice.subscribeToBooks();
EventManager.publish('The Count of Monte Cristo');
alice.unsubscribeBooks();