I've just experienced something I didn't expect at all when using class inheritance in ECMAScript Harmony.
For users of reactive frameworks this is not a concern. It is a concern for those using class inheritance across different ECMAScript modules.
Because the class's extends (as in class B extends A) clause is resolved as soon as the class declaration is evaluated, there's no way to defer its resolution in case A is declared after that class.
TypeScript will not help in anyway to declare the classes in the right order, so I'm wondering if there are any plans on mimmicking ECMAScript 4 behavior here? I believe this is impossible to resolve at ECMAScript Harmony, though.