Docker containerization in Express - Mini Project: Build & Apply

Docker containerization

📖 Scenario: You are building a simple Express.js web server that responds with a greeting message. You want to package this server inside a Docker container so it can run anywhere easily.

🎯 Goal: Create a basic Express.js app, configure it to listen on a port, write a Dockerfile to containerize the app, and add the final Docker command to run the container.

📋 What You'll Learn

Create an Express.js app with a single route '/' that sends 'Hello from Docker!'

Set the app to listen on port 3000

Write a Dockerfile that uses the official Node.js image, copies app files, installs dependencies, and exposes port 3000

Add the Docker command to run the container mapping port 3000

💡 Why This Matters

🌍 Real World

Docker helps developers package apps with all dependencies so they run the same everywhere, like on your laptop, a server, or cloud.

💼 Career

Knowing Docker containerization is essential for modern backend development, deployment, and DevOps roles.

1

Create the Express.js app

Create a file app.js with an Express.js app that imports express, creates an app instance, and sets a route '/' that sends the text 'Hello from Docker!'.

Express

// Your code here to create the Express app with route '/'

Need a hint?

Use require('express') to import Express. Create an app with express(). Use app.get to define the route.

2

Set the app to listen on port 3000

Add a line to make the Express app listen on port 3000 using app.listen(3000).

Express

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Hello from Docker!');
});

// Add app.listen on port 3000 below

Need a hint?

Use app.listen(3000) to start the server on port 3000.

3

Write the Dockerfile to containerize the app

Create a Dockerfile with these lines: FROM node:18, WORKDIR /app, COPY . ., RUN npm install express, EXPOSE 3000, and CMD ["node", "app.js"].

Express

# Your Dockerfile content here

Need a hint?

Use the official Node.js 18 image. Set working directory, copy all files, install express, expose port 3000, and set the command to run app.js.

4

Add the Docker run command

Write the Docker command to run the container named my-express-app mapping host port 3000 to container port 3000 using docker run -p 3000:3000 --name my-express-app and the image name my-express-image.

Express

# Your Docker run command here

Need a hint?

Use docker run with -p 3000:3000 to map ports and --name my-express-app to name the container.