Singleton

var Singleton = (function () {
    var instance;

    function init() {
        function privateFunction() {
            console.log("private function");
        }

        var privateRandomNumber = Math.random();

        return {
            publicFunction: function () {
                console.log("public function");
            },
            publicProperty: "public property",
            getRandomNumber: privateRandomNumber
        }
    }

    return {
        getInstance: function () {
            if (!instance) {
                instance = init();
            }

            return instance;
        }
    }
}());

var sing1 = Singleton.getInstance();
var sing2 = Singleton.getInstance();
console.log(sing1.getRandomNumber === sing2.getRandomNumber);

var SingletonTester = (function () {

    var instance;

    function Singleton(options) {
        options = options || {};
        this.name = "tester";
        this.pointX = options.pointX || 5; //default value
        this.pointY = options.pointY || 10;
    }

    var _static = {
        name: "tester",
        getInstance: function (options) {
            if (instance === undefined) {
                instance = new Singleton(options);
            }

            return instance;
        }
    }

    return _static;
}());

var sing = SingletonTester.getInstance({ pointX: 10 });
console.log(sing.pointX);