Add custom types for external libraries

Set typeRoots in tsconfig.json

"typeRoots": [                           
  "src/types", // Custom types goes here
  "node_modules/@types" // Fallback to default @types path
]

Create new type file with subdirectory name as the packages name eg. for wordcut package : src/types/wordcut/index.d.ts

declare module 'wordcut';

You can add more types to functions / variables later within {}

declare module 'wordcut' {
  function init(): void;
  function cut(s: string): string;
}

Links

• ​Typescript confusion: tsconfig.json module, moduleResolution, target & lib explained - Explain differences between module and target option in tsconfig.json