Singleton Pattern with Require JS

MySingleton.js

define(function(){
    var instance = null;

    function MySingleton(){
        if(instance !== null){
            throw new Error("Cannot instantiate more than one MySingleton, use MySingleton.getInstance()");
        } 
        
        this.initialize();
    }
    MySingleton.prototype = {
        initialize: function(){
            // summary:
            //      Initializes the singleton.
            
            this.foo = 0;
            this.bar = 1;
        }
    };
    MySingleton.getInstance = function(){
        // summary:
        //      Gets an instance of the singleton. It is better to use 
        if(instance === null){
            instance = new MySingleton();
        }
        return instance;
    };

    return MySingleton.getInstance();
});