Another take on singleton pattern in JavaScript

singleton.js

function singleton(self, wrapper, ctor) {
  // support for early failing
  if (self instanceof wrapper) {
    throw wrapper.name + " " +
      "is a singleton, you cannot create its instance. " +
      "To get the isntance: " + wrapper.name + "();";
  }

  if (!ctor) {
    return;
  }

  if (!wrapper.instance) {
    wrapper.instance = new ctor();
  }

  return wrapper.instance;
}

function Hello() {
  // fail early if called with new Hello() <- not mandatory
  singleton(this, Hello);

  function HelloCtor() {
    this.id = String(Math.random()).replace("0.", '');
    this.hi = function() { alert("Hello, World! " + this.id); };

    alert("Constructing: " + this.id);
  }

  // construct the instance or return constructed
  return singleton(this, Hello, HelloCtor);
}

// constructor should be called only once and id should be the same
Hello().hi();
Hello().hi();

// exception should be raised for new Hello()
var caught = false;
try {
  (new Hello()).hi();
} catch (ex) {
  alert("Exception caught: " + ex);
  caught = true;
}

if (!caught) {
  alert("Exception not caught when creating singleton")
}