Facebook Launches Flow, Static Type Checker for JavaScript
This looks like such a better step in the right direction than than the types of tools MS and Google have been putting out.  Dynamically discerning the underlying code, and allowing optional type annotation works _with_ javascript, as opposed to attempting to turn js into a completely different (and weakened) language.That said, I am curious what solutions this solves that isn't already solved by enforcing good code coverage.  Full disclaimer, the largest js projects I've worked on were in the tens of thousands of lines, not hundreds of thousands, but type checking just seemed completely unnecessary provided a good coding guide and test coverage were maintained and enforced.