class-2

Class 2: Express.js Project From Scratch + Docker

Live Class: 60
Duration: 90 minutes
Difficulty: Intermediate (hands-on)

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Learning Objectives

By the end of this class, you will:

1. Initialize an Express + TypeScript project from zero with npm/pnpm.
2. Set up TypeScript strict mode with path aliases for clean imports.
3. Configure npm scripts (dev, build, start, lint, format).
4. Use environment variables safely with .env and validation (Zod).
5. Implement structured logging with Pino.
6. Build a production-ready folder structure following industry patterns.
7. Write a multi-stage Dockerfile for containerization.
8. Use docker-compose to run app + MongoDB together.
9. Implement graceful shutdown (handle SIGTERM, close connections).
10. Deploy a starter project that you'll reuse for all future classes.

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Prerequisites

• Comfortable with npm/pnpm commands
• Understand Node.js basics
• Completed Class 1 (layered architecture)
• Docker and docker-compose installed
• Terminal/CLI confidence

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Agenda (90 minutes)

Time	Topic	Activity
0:00 - 0:10	Intro & Project Setup	Slides
0:10 - 0:30	npm init & TypeScript Config	Live coding
0:30 - 0:50	Folder Structure & npm Scripts	Live demo
0:50 - 1:05	Environment Variables & Logging	Code walkthrough
1:05 - 1:20	Docker & docker-compose	Live Docker build
1:20 - 1:30	Q&A & Homework Preview	Discussion

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Materials

• Speaker Outline
• 01: Project Scaffolding
• 02: Configuration & Environment
• 03: Docker & Deployment
• Demo: Production Express Starter

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Quick Start

cd code/demo-express-starter
pnpm install
pnpm dev

Visit http://localhost:3000/health and http://localhost:3000/api/docs (when ready).

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Key Concepts

##Package Scripts

{
  "scripts": {
    "dev": "tsx watch src/main.js",        // Development (auto-reload)
    "build": "tsc",                        // Compile TypeScript
    "start": "node dist/main.js",          // Run compiled app
    "lint": "tsc --noEmit",               // Check types
    "format": "prettier --write src/**/*"  // Format code
  }
}

##Environment Variables

// .env
NODE_ENV=development
PORT=3000
DATABASE_URL=mongodb://localhost:27017/taskdb
LOG_LEVEL=debug

Validate with Zod:

const envSchema = z.object({
  NODE_ENV: z.enum(['development', 'production']),
  PORT: z.coerce.number().default(3000),
  DATABASE_URL: z.string().url(),
  LOG_LEVEL: z.enum(['debug', 'info', 'warn', 'error'])
});

const env = envSchema.parse(process.env);

Docker Basics

FROM node:20-alpine
WORKDIR /app
COPY package*.json .
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "run", "dev"]
# For production
# CMD ["npm", "start"]

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Starter Project Structure

src/
  ├── main.js              ← Entry point
  ├── config.js            ← Environment config
  ├── logger.js            ← Structured logging

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Docker Commands

# Build image
docker build -t taskapp:latest .

# Run container
docker run -p 3000:3000 -e NODE_ENV=development taskapp:latest

# Using docker-compose
docker-compose up

# Build fresh
docker-compose up --build

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Common Mistakes

1. Forgetting .env → App crashes on startup (env vars undefined).
2. Not using tsx for dev → Slow development cycle.
3. Shipping node_modules in Docker → Bloated image.
4. Not validating environment → Silent bugs from typos.
5. Forgetting graceful shutdown → Requests lost on deploy.

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Quality Checklist

• ✅ pnpm dev works
• ✅ pnpm build produces dist/
• ✅ pnpm start runs production build
• ✅ docker build succeeds
• ✅ docker-compose up brings app + DB online
• ✅ curl localhost:3000/health returns { "status": "ok" }

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Interview Questions

1. Why use a multi-stage Dockerfile? — Reduces image size by excluding build tools.
2. How do you validate environment variables? — Schema validation (Zod, Joi) before app starts.
3. What's graceful shutdown? — Stop accepting requests, finish in-flight ones, then exit.
4. Why use tsx in dev? — Fast dev cycle; auto-compiles and reloads.

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Banglish Glossary

Term	Banglish	Explanation
Environment Variables	পরিবেশ ভেরিয়েবল	অ্যাপ চালানোর জন্য সেটিংস (উদাঃ পোর্ট, ডাটাবেস URL)
Docker Image	ডকার ইমেজ	আপনার অ্যাপের ব্লুপ্রিন্ট (রান করার জন্য প্রস্তুত)
Container	কন্টেইনার	চলমান ডকার ইমেজ (জিনিসের বাস্তব উদাহরণ)
docker-compose	ডকার-কম্পোজ	একাধিক সেবা একসাথে চালানোর টুল
Graceful Shutdown	সুন্দর বন্ধ	অ্যাপ চলমান কাজ শেষ করে নিরাপদে বন্ধ করা

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Support

• Demo won't run? Check Node 20 (node -v), run pnpm install.
• Docker errors? Ensure Docker daemon is running (docker ps).
• Environment validation fails? Check .env file exists and is in repo root.

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**Now let's build something production-grade. Let's go! **