This isn't strictly true, and @erikpukinskis has a point. Typed languages often do have type info that can make it to runtime. `typeof` -- virtually the only tool JS has for type reflection -- doesn't even compare to the richness of TypeScript. All of that richness is indeed lost in transpilation.

In C++, for example, we have `decltype`, `typeid`, type traits, RTTI, and so on -- all of which are available at runtime. Not to mention that in certain special cases, we also have the de facto storage of type information that makes it into binaries (e.g. discriminated union types).