TypeScript + Node.js

What this module covers

4 steps · TypeScript

1. Step 1. TypeScript + Node.js

   TypeScript works seamlessly with Node.js and Express for type-safe server code. import express, { Request, Response } from 'express'; const app = express(); app.use(express.json()); interface User { id: number; name: string; email: string; } app.get('/users/:id', (req: Request<{ id: string }>, res: Response) => { res.json({ id: req.params.id }); } ); Best practices: always install @types/node and @types/express, type route parameters/query strings/request bodies, extend Express Request for custom properties like req.user, and use tsx or ts-node for faster development.

   Express's Request and Response types come from @types/express — importing and annotating both parameters is what turns a plain JS handler into a type-checked one. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

   Check yourself: [TypeScript] Write a typed handler that responds with a status JSON object.

2. Step 2. Quiz: TypeScript + Node.js

   Answer these questions about typing an Express backend.

   @types/express provides the Request/Response types; Request is generic over route params, response body, request body, and query. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

   Check yourself: [TypeScript] Answer the quiz below.

3. Step 3. Typed Express Route

   Define PostParams (id: string) and PostBody (title, content). Write a typed updatePost handler.

   Typing both the route params and the request body on one handler is exactly what a real "update a resource" endpoint needs — this is the Express + TypeScript pattern at its most practical. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

   Check yourself: [TypeScript] Are PostParams and PostBody defined, and does updatePost use them correctly?

4. Step 4. Mini project: TypeScript + Node.js

   Define PostParams (id: string) and PostBody (title, content). Write a typed updatePost handler. Turn the completed challenge into a small standalone project. Add realistic content, clear naming, one edge case or error state, and a short README-style explanation of how the main idea works.

   Typing both the route params and the request body on one handler is exactly what a real "update a resource" endpoint needs — this is the Express + TypeScript pattern at its most practical. This project stage asks you to apply the same idea without step-by-step scaffolding. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

   Check yourself: [TypeScript] Are PostParams and PostBody defined, and does updatePost use them correctly?