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.
[TypeScript] Type Definitions and Modules
原文：https://www.cnblogs.com/Answer1215/p/10353435.html