Earlier quoted context omitted.
I haven't found any disadvantage to TypeScript over JavaScript. It's also trivial to switch, since compilation mostly just removes type annotations. I have however been annoyed at not being able to use sweet.js macros.
I'm still on an earlier version of TypeScript, so I don't know if later versions have fixed this. We ran into trouble when creating knockout view models in type script. Basically, TypeScript was losing track of 'this', and the trick of using var self=this in the the "constructor" wasn't valid. We made it work, but it wasn't pretty and it certainly wasn't idiomatic typescript. Basically the problem was that we were tr…
Yeah, you do have to know JavaScript, since TypeScript only adds a few ES6 features and types.