[TypeScript] Type Definitions and Modules

For example you are building your own module, the same as Lodash:

my-lodash.d.ts

declare module "lodash" {     declare interface FirstFunction {         (data: any[]) :any;     }      declare interface Lodash {           first: FirstFunction;     }      export const _: Lodash: }

Normally you can install @types for popluar 3rd-party libs, if you have to build your own, you need to remember export type defination aas well for Typescript.