Javascript OOP - prototype in IIF

MyObjectProrotype

    var MyObject = (function () {
        function extend(Child, Parent) {
            var F = function() { }
            F.prototype = Parent.prototype
            Child.prototype = new F()
            Child.prototype.constructor = Child
            Child.superclass = Parent.prototype
        }

        function ParentObject () {
            this.var1 = 'value1';
        }
        ParentObject.prototype.myMethod = function () {
            this.var1 = 'value_1_1';

            return this;
        }

        function ChildObject () {
            this.var2 = 'value2';
            ChildObject.superclass.constructor.apply(this, arguments);
            this.myMethod();

            return this;
        }
        extend(ChildObject, ParentObject);

        return {
            self: ParentObject,
            Child: ChildObject
        }
    })();

    var MO1 = new MyObject.self();
    var MO2 = new MyObject.Child();
    console.log('MyObjects:', MO1, MO2);