"use strict";

/**

* Singleton Pattern - Simplest pattern of all that ensures only one class

* has only one instance and it is a global property.

*

* Example - Usually for configuration settings where you don't want to create

* a chaos by having many instances of the same class

*

*/

let Singleton = (() => {

let instance = undefined;

class ConfigModule {

someReallyUsefulFunction() {

console.log("Hello World");

}

}

let getInstance = () => {

if (!instance) {

instance = new ConfigModule()

}

return instance;

}

return {

getInstance: getInstance

};

})();

let instance1 = Singleton.getInstance();

let instance2 = Singleton.getInstance();

console.log(instance1 === instance2);