How a singelton works in a static function and how it serves as a command in a class

Question

I do not know how a singleton has functionality in a class

I have tried its function and its state but it still doesn't execute the program for me if I do so.

Answer 1

Here is an example of singleton using a factory:

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 reset
                instance.constructor = null;
            }
            return instance;
        }
   };
})();


// ...

var test = SingletonFactory.getInstance();

More information available here.