As mentioned in some previous posts, TypeScript is a very useful tool (language) for writing more correct code in larger JavaScript applications, and with Angular 2 (and at least one of its competitors) built in TypeScript, TS is likely to gain a lot more popularity.
To help anyone still getting started, I have translated the sample “phonecat” application used in the AngularJS 1.x tutorial, to TypeScript. See the link below.
https://github.com/OasisDigital/phonecat-typescript