function foo() {
    if ((this instanceof foo) === false)
    {
        console.log('not an instance, hence a reference!');
        /* returns new object of this class, which will trigger runtime of this
         * function */
        return new foo();
    }
    else
        console.log('you have an instance?');
}

var ref = foo;
ref.call(ref);

var inst = new foo();