Overall, Microsoft engineers spent over two years developing this functionality, Hejlsberg said. The company released the specification of TypeScript, as well as an open source compiler on the CodePlex repository. The company also developed a TypeScript plug-in for Visual Studio.
TypeScript's type annotation is flexible as well. Developers can add type annotations only where they want it, to their own code, or to specific libraries.
Classes will allow developers to reuse existing functionality in the program. Modularity can help them organize large codebases, as well as make it easy to swap in updates to one part of the code with little impact to other parts of the program.
The TypeScript specification is available, at no cost, under the Open Web Foundation OWFa 1.0 Specification Agreement, and Microsoft is seeking community consultation for further development. The compiler is licensed under the Apache 2.0 license.