🎯 What We’ll Cover

• Setting up a basic Node.js app
• Writing a Dockerfile
• Running it in a container
• Making it accessible to the outside world

By the end, you’ll have a containerized Node.js app that works like magic (minus the wizard robes).

📦 Step 1: Create a Basic Node.js App

First, let’s set up a super simple Node.js application.

Run these commands:

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mkdir node-docker && cd node-docker
npm init -y

Now, let’s install Express (because who writes plain HTTP servers anymore?):

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npm install express

Then, create a file called server.js and paste this inside:

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const express = require('express');
const app = express();
const PORT = process.env.PORT || 3000;

app.get('/', (req, res) => {
res.send('Hello from Dockerized Node.js! 🚀');
});

app.listen(PORT, () => {
console.log(`Server is running on port ${PORT}`);
});

Boom!

Basic Node.js server ✅

🛠 Step 2: Write the Dockerfile

Now, let’s create a Dockerfile.

This file tells Docker how to build our container.

Create a file named Dockerfile (yes, no extension) and add this:

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# Use the official Node.js image as a base
FROM node:18-alpine

# Set the working directory in the container
WORKDIR /app

# Copy package.json and install dependencies
COPY package.json .
RUN npm install

# Copy the rest of the application files
COPY . .

# Expose the port the app runs on
EXPOSE 3000

# Start the application
CMD ["node", "server.js"]

This file does a few things:

1. Uses a small, efficient Node.js image (node:18-alpine)
2. Sets up a working directory
3. Copies package.json and installs dependencies
4. Copies the rest of the files
5. Exposes port 3000
6. Runs the app with node server.js

🏗 Step 3: Build and Run the Docker Container

Now that we have a Dockerfile, let’s build our image and run it.

🔨 Build the Image

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docker build -t my-node-app .

This tells Docker to build an image named my-node-app using the Dockerfile in the current directory (.).

�� Run the Container

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docker run -p 3000:3000 my-node-app

Here’s what’s happening:

• -p 3000:3000 maps port 3000 inside the container to port 3000 on your machine.
• my-node-app is the name of the image we just built.

Now, visit http://localhost:3000/, and you should see:

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Hello from Dockerized Node.js! 🚀

🐳 Extra: Running in Detached Mode

If you want the container to run in the background (so your terminal isn’t stuck), run:

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docker run -d -p 3000:3000 my-node-app

Then, to stop the container later, use:

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docker ps # Get the container ID
docker stop <container_id>

📌 Key Ideas

🔗 References

• Docker Official Docs
• Node.js Official Docs
• Express.js Official Docs