singleton pattern

gistfile1.js

var mySingleton = (function(){

  var instance = null

  function K(){
    if(!instance || this !== instance) throw "Constructor is a singleton"
    return this
  }

  K.prototype.foo = function(){}
  K.prototype.bar = function(){}
  K.prototype.bar = function(){}
  
  return function(){
    if(!instance) instance = K.call(Object.create(Constructor.prototype))
    return instance
  }
})()

gistfile2.js

function singleton(object){ 
  var instance = null
   
  return function(){
    if(!instance) instance = Object.create(object)
    return instance
  }
}

Nice code, but in my opinion, word Constructor is not usable to this situation :) this is only my opinon, at first I say wtf is this :D

@piecioshka True, that's because I decided to use Object.create afterwards. I renamed it to a generic K.