Also check out our "What's New in TypeScript" page[1] for a little more detail.
[1] https://github.com/Microsoft/TypeScript/wiki/What's-new-in-T...
Does Microsoft use TypeScript for any of its other products or web services? How strongly are Microsoft web teams encouraged to dogfood TypeScript? :)
VS Code, IE11/Edge's F12 developer tools, and Sway (Office) use it to name only a few.
VS Code's source: https://github.com/Microsoft/vscode