Different Backbone Singleton Implementations

Backbone singleton implementation 1

//code quote from http://blog.robertpataki.com/blog/2015/08/04/using-the-singleton-pattern-in-requirejs/
define([],

    function() {

        'use strict';
    
        var instance = null;
 
        function Singie() {
            if(!!!instance){
                this.initialize();
                instance = this;
            }
            window.SINGIE = instance; // Good to have reference on window
            return instance;
        };

        Singie.prototype = {
            initialize: function() {
                // Private vars
                this._hello = 'Hello';

                // Public methods
                this.sayHello = function sayHello(name) {
                    var n = name || 'Anonymous';
                    console.log(this._hello + ' ' + n);
                }
            }
        };

        return Singie;
    }
);

var singie = new Singie();
singie.sayHello('Foo');
// Will put 'Hello Foo' in the console

var singie = new Singie();
var singieClone = new Singie();
console.log(singie === singieClone);
// Will put true in the console

var singie = new Singie();
SINGIE.sayHello('Bar');
// Will put 'Hello Bar' in the console

Backbone singleton implementation 2

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();
});