We at http://www.universalsubtitles.org/en/ have. The code is open source https://github.com/pculture/unisubs/tree/dev/media/js/widget .
I'm writing a blog post about that should be up still today on our development blog.
TL;DR
It's full of good code, some interesting idea. But, tries to make Javascript feel like Java (annotated types, very verbose etc). Also makes it difficult to use other libs (specially with the compiler in advanced mode). I don't think it's a good option for most teams.