implementing TypeScript and Node.js: How to Properly Type Express Request and Response Objects?
I'm stuck on something that should probably be simple. I'm working on a Node.js application using TypeScript and Express, and I’m having trouble correctly typing the `request` and `response` objects in my route handlers. I created a simple POST endpoint to handle user registration, but I'm getting type errors when trying to access properties on these objects. Here’s what my code looks like: ```typescript import express, { Request, Response } from 'express'; import bodyParser from 'body-parser'; const app = express(); app.use(bodyParser.json()); app.post('/register', (req: Request, res: Response) => { const username: string = req.body.username; const password: string = req.body.password; if (!username || !password) { return res.status(400).json({ message: 'Username and password are required.' }); } // Simulate user creation res.status(201).json({ message: 'User created successfully!' }); }); app.listen(3000, () => { console.log('Server is running on port 3000'); }); ``` However, I’m receiving the following behavior message when I try to compile the TypeScript code: ``` Property 'username' does not exist on type 'unknown'. ``` I’ve tried using type assertions like this: ```typescript const username: string = (req.body as { username: string }).username; ``` But I feel like that’s not the right approach. What’s the best way to properly type the request body to avoid these issues? Is there a recommended way to define an interface for the expected structure of the request body? Any help would be appreciated! My development environment is macOS. What's the best practice here? This is happening in both development and production on macOS.