How to add Typescript definitions to Express req & res

You can use ES6 style named imports to import only the interfaces you need, rather than import * as express from 'express' which would include express itself.

First, make sure you have installed the type definitions for express (npm install -D @types/express).

Example:

// middleware/authCheck.ts
import { Request, Response, NextFunction } from 'express';

export const authCheckMiddleware = (req: Request, res: Response, next: NextFunction) => {
  ...
};

// server.ts
import { authCheckMiddleware } from './middleware/authCheck';
app.use('/api', authCheckMiddleware);

Currently using TypeScript 2.3.4 and @types/express 4.0.36.