You cannot yield from the global scope; you have to explicitly be inside a generator function. This isn't really a problem in practice except for one-off-scripts, since most modules don't have side effects but instead export functions (possibly generator functions). But for those one-off scripts it is indeed a bit awkward... you could imagine ways to get around it.

You can catch async errors with generators and promises; see e.g. the linked post, or http://jlongster.com/A-Study-on-Solving-Callbacks-with-JavaS...

> we cant catch async errors outside the async callback , will generators fix this ?

You can inject an exception into a generator via the throw method[0], and it'll be raised at the yield, as if `yield` had thrown[1].

JS exception handling facilities are still crap, though.

[0] http://wiki.ecmascript.org/doku.php?id=harmony:generators#me...

[1] http://wiki.ecmascript.org/doku.php?id=harmony:generators#in...

That's why node modules generally don't throw exceptions, but rather pass them as the first argument to the callback.

I think you can catch async errors if you call the throw method on the generator.

http://wiki.ecmascript.org/doku.php?id=harmony:generators#me...