Simplest/Cleanest way to implement singleton in JavaScript?

Question

What is the simplest/cleanest way to implement singleton pattern in JavaScript?

Answer 1

I think the cleanest approach is something like:

var SingletonFactory = (function(){
    function SingletonClass() {
        //do stuff
    }
    var instance;
    return {
        getInstance: function(){
            if (instance == null) {
                instance = new SingletonClass();
                // Hide the constructor so the returned object can't be new'd...
                instance.constructor = null;
            }
            return instance;
        }
   };
})();

Afterwards, you can invoke the function as

var test = SingletonFactory.getInstance();