Extend interface defined in .d.ts file

Question

In my TypeScript project, I use DefinitelyTyped definitions for external js dependencies.

Sometimes it might happen that these definitions are outdated. It might als

Answer 1

I was able to accomplish this by following the directions at https://www.credera.com/blog/technology-solutions/typescript-adding-custom-type-definitions-for-existing-libraries/. There they use the example of react.

import 'react';
 
declare module 'react' {
    interface OlHTMLAttributes<T> {
        type?: "1" | "a" | "A" | "i" | "I";
    }
}

I found this works really well for winston too.

Answer 2

// How to extend Validator interface adding isArray() method??

You cannot do this in a file that is a module (some guidance here) and your file is a module because you have import expressValidator.

Instead create a extendedValidator.d.ts and add the new stuff for TypeScript's engine:

declare module ExpressValidator {
  export interface Validator {
     isArray: any;
  }
}