You already have a working Node.js application, and now it's time to package it with Docker. While your app handles requests and responses, Docker makes sure it runs reliably in any environment—on your machine, a teammate's system, or in the cloud.

Think of your app as the engine of the project, and Docker as the container that carries everything it needs to run: your code, dependencies, and the Node.js runtime.

Creating the Dockerfile

The Dockerfile tells Docker exactly how to build an image for your Node.js application. In simple terms, it's like a recipe: step-by-step instructions for setting up the environment, installing dependencies, and running the application inside a container.

You need to create a Dockerfile in your my-app project. Make sure the Dockerfile has no file extension, as this could cause errors later. You can download the file below.

Add the following content:

Building and Running the Docker Container

Before running any commands, make sure your terminal is inside your project's root directory, for example: C:\Users\YourUsername\my-app.

Now you need to build a Docker image for our application so that it can run inside a container.

This command builds a Docker image from the Dockerfile in the current folder and tags it as my-app.

Next, you need to run our container and make it available on port 3000 so you can access it in a browser.

The -p 3000:3000 flag maps port 3000 inside the container to port 3000 on your local machine. This makes the application accessible through your browser.

Open a browser and go to:

Here, localhost refers to your own computer, and 3000 is the port where the application is listening.

If everything is set up correctly, you should see:

This confirms the Node.js server is running inside the Docker container. The application is now portable and will run the same way on any system with Docker installed.