Everyone wants to play a major role in (r)evolution of JavaScript. CoffeeScript (http://coffeescript.org/) has already gained some popularity, Google has released its Dart (http://www.dartlang.org/) not that long time ago. Here comes Microsoft (have you noticed that they are always late?), bringing to you…

TADAMMM!
And actually it’s a good stuff (would I bother you if it were otherwise? ;>). What’s so special about it?

  1. It’s a "strict superset" of JavaScript. That means that every valid JavaScript code is also a valid TypeScript code (so it’s just extends the core syntax, doesn’t substitute it with completely new one).

  2. It doesn’t need any additional runtime to run (why? check the prev point).

  3. It introduces static typing (YAY!), classes (wow) and interfaces (WOW).

  4. Thanks to static typing, it’s far easier to get code completion (IntelliSense) or do more sophisticated code analysis.

  5. It’s open source.

  6. It’s self-hosting already (TypeScript compiler is written in TypeScript).

The cool thing is that TypeScript doesn’t have many drawbacks - one worth mentioning is the poor tooling (for now) outside of Windows.

If you want to make your own opinion on TypeScript, here are few interesting links: