Express-jwt middleware typescript types issue

Question

I am trying to implement an express API that authenticates via a jwt token and I'm using the express-jwt middleware to authenticate access to a method:

import express from 'express'
import jwt from 'express-jwt'

const app = express()

app.get('/protected', jwt({ secret: 'jwtSecret', algorithms: ['HS256'] }), prot)

const prot = (
    req: express.Request,
    res: express.Response,
    _next: express.NextFunction
): void => {
    res.json({
        msg: req.user,
    })
}

app.listen(3000)

But I get this error:

Property 'user' does not exist on type 'Request<ParamsDictionary, any, any, ParsedQs>'.ts(2339)

I've tried attaching req: express.Request & { user: unknown }, but then the function doesn't fit with express anymore.

Any ideas what I can do here. If worse comes to worse, can I just tell TypeScript to shut up somehow, since I know that the field will be there (even though I know that's not the point of TypeScript)

Answer 1

user is not an existing property on req object. You can make your own typings for req object by creating a .d.ts file on your project, for example, create a express.d.ts file and it will contains:

declare namespace Express {
   export interface Request {
       user: SomeType
   }
}

Demo: https://repl.it/repls/OldlaceWhoppingComputationalscience

Try deleting the express.d.ts and the error will appears again.

Answer 2

declare global {
  namespace Express {
    interface Request {
      user?: UserPayload;
    }
  }
}

this is an example of UserPaylaod

  interface UserPayload {
     id: string;
     email: string;
   }