I shouldn't have included nominal typing - it seems the instanceof operator actually works, e.g. see http://stackoverflow.com/questions/24705631/typescript-myob

I shouldn't have included nominal typing - it seems the instanceof operator actually works, e.g. see http://stackoverflow.com/questions/24705631/typescript-myobject-instanceof#24707830 http://stackoverflow.com/questions/24705631/typescript-myobj.... But in TS itself structural typing is used everywhere for actual type checking (except for classes with private members), and from my understanding there's no way to have TS help you check at runtime whether a type is structurally compatible with a value.