[dodyg]

Try the TypeScript playground http://www.typescriptlang.org/Playground/ . You can do rename, intellisense, find reference, etc directly from your browser.

TypeScript language service is developed in TypeScript. This is how they can host these type of function on the browser. It's all just JavaScript

Check out this screenshot from the playground http://i.imgur.com/H2rqD.png

[jmmcd]

Typescript has static type annotations. All those things are already easy in that context.