TypeScript lets you write JavaScript the way you really want to.
TypeScript is a typed superset of JavaScript that compiles to plain JavaScript.
Any browser. Any host. Any OS. Open Source.
Ref:http://definitelytyped.org
Ref:http://www.typescriptlang.org
Ref:http://www.typescriptlang.org/Handbook
Ref:https://github.com/Microsoft/TypeScript/blob/master/doc/spec.md