[megaupload]

class Animal {
    animal = 'animal';

    say() {
        alert('i animal')
    }
}


class Cat extends Animal {
    cat = 'cat';

    say() {
        super.say();
        alert('and i cat')
    }
}

new Cat().say();

а получается так

var __extends = this.__extends || function (d, b) {
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};
var Animal = (function () {
    function Animal() {
        this.animal = 'animal';
    }
    Animal.prototype.say = function () {
        alert('i animal');
    };
    return Animal;
})();
var Cat = (function (_super) {
    __extends(Cat, _super);
    function Cat() {
        _super.apply(this, arguments);

        this.cat = 'cat';
    }
    Cat.prototype.say = function () {
        _super.prototype.say.call(this);
        alert('and i cat');
    };
    return Cat;
})(Animal);
new Cat().say();
//@ sourceMappingURL=td.js.map