How to add Typescript definitions to Express req & res

Question

I have a set of controller functions for my REST API and I\'m getting lots of the following

error TS7006: Parameter \'req\' implicitly has an \'any\' type.
         


        

Answer 1

It can be daunting to type the arguments every time you need to write middleware functions so you can just type the whole function directly too.

npm i @types/express --save-dev ("@types/express": "^4.17.0")

After installing typings..

// This can be shortened..
import { Request, Response, NextFunction } from 'express';
export const myMiddleware = (req: Request, res: Response, next: NextFunction) => {
  ...
};

// to this..
import { RequestHandler } from 'express';
export const myMiddleware: RequestHandler = (req, res, next) => {
  ...
};

// or in case it handles the error object
import { ErrorRequestHandler } from 'express';
export const myMiddleware: ErrorRequestHandler = (err, req, res, next) => {
  ...
};