Backend Practice Lab — TypeScript and Node.js

This is a shared hands-on path for the study guides. It is added teaching material, not a claim about any one video.

The guides now use a small TypeScript/Node.js service as the common learning project. You will keep one project and improve it as you move through the playlist instead of reading isolated snippets.

1. Create the project

mkdir backend-practice-lab
cd backend-practice-lab
npm init -y
npm install fastify zod
npm install --save-dev typescript tsx @types/node
npx tsc --init

Why these packages:

• Fastify provides the HTTP server and routing used by the examples.
• Zod validates external input at the API boundary.
• TypeScript catches many shape mistakes before the program runs.
• tsx runs TypeScript during learning without a separate compile step.

Add these scripts to package.json:

{
  "scripts": {
    "dev": "tsx watch src/server.ts",
    "start": "tsx src/server.ts",
    "typecheck": "tsc --noEmit"
  }
}

2. Use this starting server

Create src/server.ts:

import Fastify from "fastify";

export const app = Fastify({
  logger: true,
});

app.get("/health", async () => {
  return {
    ok: true,
  };
});

async function start() {
  try {
    await app.listen({
      host: "0.0.0.0",
      port: 3000,
    });
  } catch (error) {
    app.log.error(error);
    process.exit(1);
  }
}

void start();

Run it:

npm run dev
curl http://localhost:3000/health

You should receive:

{
  "ok": true
}

3. Understand every part

• Fastify creates one application object. Routes, hooks, logging, and shutdown all belong to it.
• app.get registers a handler for an HTTP GET request.
• The handler returns a JavaScript object; Fastify serializes it as JSON.
• host 0.0.0.0 allows the server to receive container/dev-environment traffic. For a local-only experiment, localhost is also reasonable.
• The try/catch makes startup failure visible. A service that cannot bind its port should not pretend it is healthy.
• void start makes it explicit that the asynchronous startup function is intentionally launched.

4. Suggested project layout

backend-practice-lab/
  src/
    server.ts             creates the HTTP application
    routes/               maps HTTP requests to controllers
    controllers/          translates request/response concerns
    services/             business rules and use cases
    repositories/         database/cache access
    plugins/              validation, auth, error handling
  tests/
  package.json
  .env.example            names required variables, never real secrets

Do not create every folder on day one. Add a folder when the corresponding lesson needs it. The point is to learn responsibility boundaries, not to copy a “clean architecture” template.

5. Your repetition loop

For every study guide:

1. Read the video note first.
2. Copy the guide’s code into this lab.
3. Run the smallest happy-path request.
4. Trigger the failure case named in the guide.
5. Write one test before moving on.
6. Only then read the production section and explain the trade-off in your own words.

6. Important safety rules

• Never commit .env files or real credentials.
• Use a separate local/test database, not data you care about.
• Keep code examples small enough that you can type them and change them.
• A snippet is not automatically production-ready; the guide tells you what must change before a real deployment.