singleton pattern

singleton.js

/*
 * http://blog.mgechev.com/2014/04/16/singleton-in-javascript/
 *
 * - It instantiates only a single object
 * - Its safe – it keeps the reference to the singleton inside a variable, which
 *   lives inside a lexical closure and is not accessible by the outside world
 * - It allows you to initialize the singleton with some arguments. The module
 *   pattern, which wraps the singleton is not aware of the initialization
 *   arguments – it simply forwards the call with apply
 * - You can use the instanceof operator
 *
 */

var MySingleton = (function () {

  var INSTANCE;

  function MySingleton(foo) {
    if (!(this instanceof MySingleton)) {
      return new MySingleton(foo);
    }
    this.foo = foo;
  }
  MySingleton.prototype.bar = function () {
    console.log("bar(): this.foo:", this.foo);
  };
  MySingleton.prototype.setBar = function (val) {
    this.foo = val;
  };

  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;
    }
  };

}());


(function() {
  "use strict";

  var myObj = MySingleton.init('example');
  myObj.bar();

  var myObj2 = MySingleton.init('example2');
  myObj2.bar();

  var myObj3 = MySingleton.getInstance();
  myObj3.bar();

  myObj.setBar("EXAMPLE");
  myObj.bar();

})();