Re:Office 365 is being completely rewritten in JavaScript
by randomname2 on Wednesday June 13, 2018 @09:34AM
(#17302858)
The linked Twitter thread states that they do use TypeScript: https://twitter.com/TheLarkInn/status/1006861097729585154
The old Javascript were very bad, recent Javascripts were bad, today's Javascript are OK, future Javascript / TypeScript is actually pretty decent.
Of course I do hope something else has taken its place.