TypeScript Academy · Lesson

Typing Express Request and Response

Extend Express types for typed route parameters and bodies.

Lesson 2 of 413 steps

Typing Express Request and Response is a free TypeScript Academy lesson on CoddyKit. This is lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the TypeScript Academy learning path, and your progress syncs across the web and the CoddyKit app. The TypeScript Academy course includes 4 lessons in total.

Welcome

Express has TypeScript types via @types/express. Learn how to make routes type-safe.

Installing Types

Install Express with its type definitions.

npm install express
npm install --save-dev @types/express

Basic Route Types

Import Request and Response from express.

import { Request, Response } from 'express';
app.get('/users', (req: Request, res: Response) => {
  res.json({ users: [] });
});

Typed Route Parameters

Type path parameters using generics on Request.

interface Params { id: string; }
app.get('/users/:id', (req: Request<Params>, res: Response) => {
  const { id } = req.params;
});

Typed Request Body

Type the request body with the RequestBody generic.

interface CreateUser { name: string; email: string; }
app.post('/users', (req: Request<{}, {}, CreateUser>, res: Response) => {
  const { name, email } = req.body;
});

Typed Query Params

Type query string parameters.

interface Query { page?: string; limit?: string; }
app.get('/users', (req: Request<{}, {}, {}, Query>, res: Response) => {
  const page = parseInt(req.query.page ?? '1');
});

Extending Request

Add custom properties to Request via module augmentation.

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

Typed Response

Chain generics on Response to type the JSON body.

app.get('/me', (req: Request, res: Response<User>) => {
  res.json(req.user!); // response body must be User
});

Error Handler Types

Express error handlers have a specific 4-parameter signature.

import { ErrorRequestHandler } from 'express';
const errHandler: ErrorRequestHandler = (err, req, res, next) => {
  res.status(500).json({ error: err.message });
};

Using Router with Types

Type a Router the same way as the main app.

import { Router } from 'express';
const router = Router();
router.get('/:id', (req: Request<{ id: string }>, res) => {});

Validation Middleware

Use a typed middleware to validate and narrow request types.

function parseBody<T>(schema: ZodSchema<T>) {
  return (req: Request, res: Response, next: NextFunction) => {
    req.body = schema.parse(req.body);
    next();
  };
}

Quick Check

What is the main benefit of using @types/express in a TypeScript project?

Answer it in the interactive lesson

Recap

Typing Express Request and Response: type Request/Response generics for params, body, and query. Extend Request via module augmentation for custom properties. Type middleware and error handlers with their specific signatures.

Free to start

Learn TypeScript with an AI tutor — free

Write and run real code in your browser, get instant help from a 24/7 AI tutor, and pick up where you left off on the web or in the app.

Courses: 101
Lessons: 352

Start learning free View the full course

Frequently Asked Questions

Is the “Typing Express Request and Response” lesson free?

Yes — the full text of “Typing Express Request and Response” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the TypeScript Academy course, upgrade to CoddyKit PRO. The TypeScript Academy course includes 4 lessons in total.

What will I learn in “Typing Express Request and Response”?

Extend Express types for typed route parameters and bodies. You practise TypeScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start TypeScript Academy?

No prior experience is required. TypeScript Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “Typing Express Request and Response” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this TypeScript Academy lesson?

Yes. Every TypeScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

← Back to TypeScript Academy