Would the same people that originally wrote the code be doing the conversion? Is it code that was written in a few months or over the course of five or more years? Is the functionally the code provide well documented or is the code itself the documentation? Is there automated testing that can help ensure things still work properly?

I'm sure you see where I'm going with this. :)

I'd say absolutely yes, it is.

I wrote up my experiences learning TypeScript here:

https://blog.isquaredsoftware.com/2019/11/blogged-answers-le...

Thanks for sharing this!