Very simple implementation of the singleton pattern in requirejs

singie.js

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() {                
                this.hello = 'Hello'
                this.world = 'World'

                this.sayHello = function sayHello() {
                    return this.hello + ' ' + this.world;
                }
            }
        };

        return Singie;
    }
);

To use the singleton instance:

_this.singie = new Singie();
console.log(_this.singie.sayHello());

// Should pop 'Hello World' in the console

To test if it is indeed a sole singleton instance:

_this.singieClone = new Singie();
console.log(_this.singie === _this.singieClone);

// Should be true