Inheritance Model

//Helper function to 'extend' prototypes
var __extends = this.__extends || function (d, b) {
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};

//Base class with a single function defined
var BaseClass = (function () {
    function BaseClass() { }
    BaseClass.prototype.calc = function (x, y) {
    };
    return BaseClass;
})();

//Child class with the function overwritten.
//It calls the base class function in the
//context of 'this', so the base class
//function can actually access members of
//the child class when called.
var ChildClass = (function (_super) {
    __extends(ChildClass, _super);
    function ChildClass() {
        _super.apply(this, arguments);

    }
    ChildClass.prototype.calc = function (x, y) {
        var z = _super.prototype.calc.call(this, x, y);
    };
    return ChildClass;
})(BaseClass); //Notice the base class 'inheritance'