Introduction
As defined, TypeScript is a superset of JavaScript that is designed to build large, scalable, enterprise Web applications. TypeScript is free, open-source, and licensed under the Apache 2 License. TypeScript runs in any Web browser, any host, and any operating system.
The current version of TypeScript is 2.3. Here is a list of recent versions and the features introduced in these releases.
V2.0 – Nullable types, discriminated unions
V2.1 – Downlevel Async/await, mapped types
V2.2 – Mixin classes, quick fixes
V2.3 – Type check .js files, Plug-in support
Here is a complete list of new features.
In this video, Andres Hejlsberg talks and demonstrates new TypeScript features added and announced at MS Build.