TypeScript has these and they're marvelous. They make writing functional style code very enjoyable and not having to capture `this` yourself is alone justification for this developer to never go back to pure JavaScript.
Might you go back when ES6 is widely supported by browsers / Node? I don't mind either way, but since the parent comment mentioned that arrow functions were coming to JS, it was interesting that you specifically said 'never', rather than 'until ES6'.
Yeah I realize that may not have been the clearest statement, thanks. While ES6 is nice, it just doesn't have the elegance and utility of some of the other TypeScript things like generics and the interfacing system.
Also, it will probably be a long time until it can be widely used, given the existence of certain browsers and versions.