var Singleton = (function () {
  var instantiated;
  function init() {
    // singleton here
    return {
      publicMethod: function () {
        console.log('hello world');
      },
      publicProperty: 'test'
    };
  }
  return {
    getInstance: function () {
      if (!instantiated) {
        instantiated = init();
      }
      return instantiated;
    }
  };
})();

// calling public methods is then as easy as:
Singleton.getInstance().publicMethod();

In conventional software engineering, the singleton pattern can be implemented by
creating a class with a method that creates a new instance of the class if one doesn't exist. In the event of an instance already existing, it simply returns a reference to that object.

Javascript Singleton Pattern

design

JavaScript