If you're just here to copy and paste, here's the final Dockerfile that will produce an image for your Express.js app:
FROM node:22.10.0-alpine.3.19
LABEL maintainer="jonas@sliplane.io"
WORKDIR /app
COPY package* ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["node", "index.js"]
And here's the .dockerignore file you should use:
node_modules
npm-debug.log
To build and run the image, use these commands:
docker build -t express-app .
docker run -p 3000:3000 express-app
Not just here to copy and paste? Let's go over what's happening in the Dockerfile!
The Setup
For this tutorial, I assume you have an Express.js project set up. Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. If you have a different setup, you might need to adjust the Dockerfile accordingly.
Typically, you'd run npm install and then node index.js to work locally. For deployment, we'll use a similar approach but within a Docker container.
Let's dive into the details of the Dockerfile.
The Dockerfile
FROM node:22.10.0-alpine.3.19
LABEL maintainer="jonas@sliplane.io"
WORKDIR /app
COPY package* ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["node", "index.js"]
So what's happening here?
- Base image:
- Uses Node.js 22.10.0 on Alpine 3.19, providing a lightweight base image.
- The
LABELinstruction adds metadata to the image.
- Working directory:
- Sets up
/appas the working directory for subsequent instructions.
- Sets up
- Dependency installation:
- Copies
package.jsonandpackage-lock.json(if it exists) to the working directory. - Runs
npm installto install dependencies.
- Copies
- Application code:
- Copies the rest of the application code into the container.
- Port exposure:
- Exposes port 3000, which is typically used by Express.js applications.
- Start command:
- Specifies the command to run the application using
node index.js.
- Specifies the command to run the application using
This approach is simpler than the multi-stage build we used for Astro, as Express.js applications typically don't require a separate build step.
Make sure to add the .dockerignore file to ignore the node_modules folder and npm debug logs. This will speed up the build process and reduce the image size.
Deployment
You can deploy this Docker container to any cloud provider that supports Docker. For example, you could use platforms like Heroku, DigitalOcean, or AWS ECS. Because I am the co-founder of Sliplane, I will show you how to deploy it there.
After signing up, you can create a new service by selecting your Github Repository. Then just keep the default settings and click on deploy.
After deployment, your Express.js app will be available under a subdomain of sliplane.app, usually it's just your service name.
You can also see the logs of your app, see metrics such as CPU and memory usage, add persistent storage, and much more. Whenever you push to your repository, Sliplane will automatically deploy your app.
If you want to try out Sliplane, the first 2 days are free! Try it out and let me know what you think :)
Deploy ExpressJS in 2 Minutes 🚀
Next Steps
Is there anything else you want to know? Do you need help dockerizing your Express.js app? Do you need help deploying it to a specific platform? Feel free to reach out!
You can find me on X or just comment here on this blog.
Cheers,
Jonas
Top comments (17)
it's also a good practice to switch add
USER nodein the Dockerfile, so as your in-docker runtime was not the root user. If I am not mistaken, you also need to runRUN chown -R node /appso as thatnodeuser had write access to the app.Yes! 100% true
Great One Jonas!
Thanks:)
Good one! :-) Any thoughts on express vs h3? 👀
I don't think I've ever used h3, but the website is sleek so it must be good xD
One basic question always bother me.
Let's say I want to deploy my NodeJs project on hostinger vps, so without using docker approach I will install NodeJs MySQL express etc and then I will pull code from my repo and install dependency and then start pm2.
But Now let's say my manager asked me to implement docker, I will create the docker image then container and then let say I deployed that container, now what?
Now that container contain my entire code?
Like I won't need pull from the GitHub to bring my whole code into my VPS?
Or I would just run docker there?
Means I won't be having code on server? Just docker file or what?
I had the same question when I first was introduced to docker. What is it good for? As a front end developer doing react its not really important. As a full stack developer it opens doors.
Question:
"Now that container contain my entire code?"
Answer:
Yes and no.
Once you build your docker image, think of that like your build of a computer operating system with all its dependencies. You aren't going to build a whole windows operating system with hardware drivers, microsoft office, email etc. You are building the equivalent of a node dist folder ( but - for full stack, not just front end code ). The bare minimum of production ready dependencies.
1 Dockerfile = build image
You might build nginx and react app in one Dockerfile because nginx is going to serve the static build content of your react production code.
2 Dockerfiles = 2 build images, that will communicate with each other over docker network.
You might build nextjs server which runs on port 3000 and nginx which runs on port 80. Nginx is reverse proxy to nextjs server because they run on separate ports. Here you have two separate Dockerfiles images built but a docker compose file which works them together, or if you were deploying these to a cloud service like aws, intead of a docker compose file you have a task definition file respectively.
Answer yes:
Yes it contains your build image.
Yes it does once you built your image:
docker build myproject . -t myproject:versionXmyproject:versionX contains all your "BUILD" code per Dockerfile. That can be deployed to the docker registry.
Answer no:
That being said, all that above is your deployed code. You still need to store your development code.
Question:
"Like I won't need pull from the GitHub to bring my whole code into my VPS?"
No. You may have built your production code and stored that in docker registry or other cloud hosting space like amazon ecr, but you have not stored your development code. Ie your Dockerfile and all your development code. That all needs to be under revision control.
Question:
So why use docker at all?
Dockerfile does a few things:
npm run myscript -- --someEnvVar value, docker does similardocker run myImage env someEnvVar myImg:versionI hope I answered the question.
nice reply! thanks for the long explanation, i hope that helps Saqib:)
Hi! Your Dockerfile will basically be the description of the steps you did without docker. You would install Nodejs (using a baseimage), copy the code, install dependencies etc the same, but Docker would do that when you build your image. Your image will then contain the final state of your files basically, which you can use to then run a container. Does that make sense?
Nicely done Jonas, but can you deploy some docker-compose file on sliplane?
Thank you, no not yet!
Nice content
Thanks:)
hono > express
fair
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