Return type for Express routes with TypeScript

Question

I'm trying to use TypeScript to it's full potential, so I avoid any if possible.

I've seen Express routes defined like this:

import { Request, Response } from "express";

myRouter.route("/foo").post((req: Request, res: Response): Response => {
  return res.send("Hello World");
});

That works because send() returns an express Response.

But if I do a redirect:

myRouter.route("/bar").post((req: Request, res: Response): Response => {
  return res.redirect("/baz");         // redirect() returns void!
});

That won't compile because redirect() returns void, not Response.

Options:

• The easy fix is to make the route return any, but I want to avoid that if possible
• I've seen code that does as unknown as Response but that seems like a hack

What is the correct way to declare routes' return types, without using any?

Answer 1

As per @jfriend's comments, the callback's declaration for RequestHandler is:

(req: Request, res: Response, next: NextFunction): any;

So using any in this case is okay.

However, declaring it as void may be even better as Express doesn't expect a return value. That's what I'm doing, and I'm considering the typings here to be "wrong" (if this isn't the case and there is a valid use case, please let me know).