TypeScript Will Kill CoffeeScript and Dart
Microsoft created a new lang: TypeScript.
TypeScript is a superset of JavaScript that combines type checking and static analysis, explicit interfaces, and best practices into a single language and compiler.
Since it's a superset of JavaScript, any JavaScript code is also a valid TypeScript code. It's also open source! The designer is Anders Hejlsberg (born 1960), father of Turbo Pascal, Delphi, Microsoft C#.
This is a great video intro, Anders Hejlsberg: Introducing TypeScript

- 2021-12-04 video gone
- http://media.ch9.ms/ch9/c3e5/e5e02f2e-5962-48db-9ddd-85e27a4fc3e5/IntroducingTSAndersH_512.jpg
- http://media.ch9.ms/ch9/c3e5/e5e02f2e-5962-48db-9ddd-85e27a4fc3e5/IntroducingTSAndersH_mid.mp4
- http://media.ch9.ms/ch9/c3e5/e5e02f2e-5962-48db-9ddd-85e27a4fc3e5/IntroducingTSAndersH.webm
- TypeScript home page: http://typescriptlang.org/
TypeScript: JavaScript Development at Application Scale By S Somasegar. At http://blogs.msdn.com/b/somasegar/archive/2012/10/01/typescript-javascript-development-at-application-scale.aspx
Note: Nicholas C Zakas worked at Yahoo as lead engineer on JavaScript for a number of year, and is the author of Professional JavaScript for Web Developers, 2012, by Nicholas C Zakas