Many non-trivial libs are typed improperly, even when they can be done right. There's massive abuse of "any" type the moment anything gets semi-challenging. Also, a non-trivial amount of type definitions don't work in strict mode, which make things worse.
Anything involving complicated higher order functions (like lodash/ramda's curry), or having a single method that can be used in various ways that don't fit well with TS' overloading mechanisms are often done wrong or poorly. Flow is a bit better at this, but the techniques it provides are not always well known, so the type definitions aren't that much better.
Anything involving complicated higher order functions (like lodash/ramda's curry), or having a single method that can be used in various ways that don't fit well with TS' overloading mechanisms are often done wrong or poorly. Flow is a bit better at this, but the techniques it provides are not always well known, so the type definitions aren't that much better.