eons ago, I migrated a frontend to Typescript and caught a lot of type-related bugs[1]. It was a 5kLoC, fast-moving productized prototype written by a team of 5. I won't ever do dynamic-typed plain Javascript in a team ever again, type-checker is superior to human code-reviews when it comes to catching potential bugs. Then again I prefer codebase stability of clever code or "expressiveness"

1. 20% were type-coercion bugs, 30% were non-boolean values being passed to boolean-named fields (with some overlap with the former). Linters have come a long way, but compile-time type-checking is better in almost every way.