Singleton Class - Javascript Solution

singleton_class.js

var mySingleton = (function () {
  // Instance stores a reference to the Singleton
  var instance;
  function init() {
    // Singleton
    // Private methods and variables
    function privateMethod(){
        console.log( "I am private" );
    }
    var privateVariable = "Im also private";
    var privateRandomNumber = Math.random();
    return {
      // Public methods and variables
      publicMethod: function () {
        console.log( "The public can see me!" );
      },
      publicProperty: "I am also public",
      getRandomNumber: function() {
        return privateRandomNumber;
      }
    };
  };
  return {
    // Get the Singleton instance if one exists
    // or create one if it doesn't
    getInstance: function () {
      if ( !instance ) {
        instance = init();
      }
      return instance;
    }
  };
})();



(function(global) {
  "use strict";
  var MySingletonClass = function() {

    if ( MySingletonClass.prototype._singletonInstance ) {
      return MySingletonClass.prototype._singletonInstance;
    }
    MySingletonClass.prototype._singletonInstance = this;

    this.Foo = function() {
      // ...
    };
  };

var a = new MySingletonClass();
var b = MySingletonClass();
//a === b
global.MySingleton = a; //or b

}(window));


var MySingleton = (function () {

  var INSTANCE;

  function MySingleton(foo) {
    if (!(this instanceof MySingleton)) {
      return new MySingleton(foo);
    }
    this.foo = foo;
  }
  MySingleton.prototype.bar = function () {
    //do something;
  };

  return {
    init: function () {
      if (!INSTANCE) {
        return INSTANCE = MySingleton.apply(null, arguments);
      }
      return INSTANCE;
    },
    getInstance: function () {
      if (!INSTANCE) {
        return this.init.apply(this, arguments);
      }
      return INSTANCE;
    }
  };

}());