TypeScript, the evolution of JS

TypeScript is a free programming language, developed and maintained by Microsoft. It's a superset of JavaScript that adds static typing and class-based objects. Anders Hejlsberg, designer of C# and creator of Turbo Pascal, has worked on its development. It can be used to build JavaScript applications that run both on the client and on the server.

It extends JS syntax

TypeScript extends JavaScript syntax, so any existing JavaScript code should work without issues. It’s designed for large projects, which get translated to plain JavaScript through a TypeScript compiler.

TS supports definition files with information about the types of existing JavaScript libraries, similar to C/C++ header files that describe the structure of existing object files. This lets other programs use the values defined in those files as if they were statically typed entities. Headers exist for popular libraries such as jQuery and the core Node.js modules.

A compiler written in itself

The compiler is written in TypeScript itself, compiles to JavaScript, and is licensed under Apache 2.

TS has been included as a first-class language in Microsoft Visual Studio since the 2013 Update 2 release, alongside other Microsoft languages. An official extension lets Visual Studio 2012 support it too.