class Base {
    public myVar:string = 'Base';
    public constructor() {
        console.log(this.myVar);
    }
}
class Child extends Base {
    public myVar:string = 'Child';
}
var base:Base = new Base(); // 'Base' - As expected
var child:Child = new Child(); // 'Base' - I would've expected this to be 'Child'
console.log(base.myVar); // 'Base' - As expected
console.log(child.myVar); // 'Child' - As expected

function Child() {
    _super.apply(this, arguments);
    this.myVar = 'Child';
}

class Base {
    public myVar:string = 'Base';
    public constructor() {
        this.setup();
    }
    protected setup() {
        console.log(this.myVar);
    }
}
class Child extends Base {
    public myVar:string = 'Child';
    public constructor() {
        super();
        this.setup();
    }
}
var base:Base = new Base(); // 'Base'
var child:Child = new Child(); // 'Child' - Now as expected
console.log(base.myVar); // 'Base'
console.log(child.myVar); // 'Child'