TypeScript: файлы деклараций (`.d.ts`) — пример кода

// Typing an untyped third-party module, properly (not just `any`)
declare module 'color-namer' {
  interface Match { name: string; hex: string; distance: number }
  interface Result { ntc: Match[]; basic: Match[] }
  export default function namer(color: string): Result;
}

// Adding a typed field to a request through your middleware chain
// authed.d.ts
import 'express';
declare module 'express-serve-static-core' { // express's real type home
  interface Request {
    user?: { id: string; roles: string[] };
  }
}
export {}; // ensure this file is a module so `declare module` augments