Do you have any concrete examples? I would argue that a complex project that is already in TS benefits more from remaining in TS, so I’m curious what your reasoning was.
1) Import/export syntax hell. This project is 148 Javascript files, 12k LOC. Everything runs in both Node and Browser environments. Without TypeScript I just use CommonJS syntax and rewrite the scripts on the fly via a server-side pass through for a browser environment. But because of the module hell (import/export/script modules/relative vs absolute paths/defaults) I couldn't find a good formula for write once, run everywhere for this large project. I needed to be outputting 2 different builds to 2 different places which led to all kinds of path problems. This is very much unique to this project though, which has unique runtime require requirements.
2) Compile time overhead when iterating. For many visual development tasks it just takes too long to change something, compile and see results in the browser. Without TS it's 0 latency. With TS it was a few seconds. Without TS I could make 10 changes with 2 seconds latency, and perhaps I make 1 type mistake costing me 20 seconds of debug time, for a total of 40 seconds. With TS I make 10 changes with 5 seconds latency and zero mistakes but now total overhead if 50 seconds. I want to be able to get the documentation and static type checking benefits without giving up that instant feedback.
Do you have any concrete examples? I would argue that a complex project that is already in TS benefits more from remaining in TS, so I’m curious what your reasoning was.