[javascript patterns] Singleton.

gistfile1.js

// first realization: self-defining function
var Universe = function () {
  var instance;
  Universe = function () {
    return instance;
  };
  Universe.prototype = this;
  instance = new Universe();
  instance.constructor = Universe;
  // other functionality below...
  instance.start = 0;
  instance.finish = 100;
  return instance;
};

// second realization: immediate function
var Universe;
(function () {
  var instance;
  Universe = function () {
    if (instance) {
      return instance;
    }
    instance = this;
    this.start = 0;
    this.finish = 100;
  };
}());