> Apparently Script# is quite mature now, and is being used to compile very large apps to JavaScript. This is a big vote of confidence from Microsoft regarding JavaScript as a compilation target.
I'd say the same thing about Google's own Closure, which they oddly enough don't mention alongside CoffeeScript et al.
I see Dart as a rethinking of much of Closure so I don't quite get what Microsoft thinks the difference between their Script# and Dart/Closure is.
Did you mean Google Web Toolkit? That compiles Java to JS, and is similar to Script# (which compiles C# to JS). Whereas Closure Compiler is an optimizing compiler for JS, it compiles JS to (better) JS. (The Microsoft article did mention Google Web Toolkit, which was nice of them.)
GWT and Script# are both quite mature at this point, it looks like. Very interesting stuff. (However, GWT is probably losing focus inside Google to Dart, so I am not sure of its long-term prospects. It's open source though so anyone can continue it if they want.)
Closure compiler doesn't just compile vanilla JS. It supports type annotations in comments and will use those to generate code. It's type system supports classes and interfaces. The Closure library has support for class-style inheritance.
Programming in Closure-style JS feels like you're using an optionally-typed class-based language, just one with really terrible syntax.
I'd say the same thing about Google's own Closure, which they oddly enough don't mention alongside CoffeeScript et al.
I see Dart as a rethinking of much of Closure so I don't quite get what Microsoft thinks the difference between their Script# and Dart/Closure is.