Node.js Singleton pattern

singleton.js

'use strict';

var singletonLock = {},
    instance;

function MySingleton(lock) {
    if (!(lock instanceof singletonLock)) {
        throw new Error('This is a singleton, do not initiate!');
    }
}

MySingleton.getInstance = function () {
    return instance || (instance = new MySingleton(singletonLock));
};

module.exports = MySingleton;