Comment by chowes

Check out http://jlongster.com/A-Study-on-Solving-Callbacks-with-JavaS... and the follow up post. It's easy enough to start using generators alongside your existing async solution (callbacks or promises).

Proxies can be used for data-binding, similar to Object.observe.

I've also yet to find a case where I need WeakMaps instead of an Object or Map. All the benefits seem to be a bit too theoretical, but I likely haven't dug into it hard enough.