As a Senior DevOps Engineer and Docker Captain, my daily activities not only focus on optimizing deployment workflows but also ensuring that our development practices are up to date with the latest standards. One critical area in modern software development is managing JavaScript packages that are compatible with both ECMAScript Modules (ESM) and CommonJS (CJS). In this article, I’ll share some of my insights and tips on how to effectively maintain dual-module packages.

Understanding Module Types and Their Impacts

It’s paramount to grasp the fundamental differences and applications of ESM and CJS formats to fully leverage their benefits in project environments. ESM, being the standard in the ECMAScript community, offers advantages in terms of asynchronous loading and static tree shaking, while CJS is widely used for its simplicity and broad compatibility in Node.js environments.

Avoiding “Type: module” in Dual-Compatible Libraries

When setting up a library that supports both ESM and CJS, it’s advisable to avoid explicitly defining "type": "module" in your package.json. This setting restricts the package to only support ESM, which could lead to compatibility issues with projects expecting CJS modules. Instead, utilize the main and module fields to differentiate between entry points, ensuring that both module types are accessible based on the consumers’ configuration.

Example Configuration for a Dual-Compatible Package

Here’s a practical example of how to configure a package to support both module types seamlessly:

  "name": "example-library",
  "version": "1.0.0",
  "description": "A simple library demonstrating dual module compatibility",
  "main": "dist/index.cjs",
  "module": "dist/index.mjs",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  "keywords": ["esm", "cjs", "javascript"],
  "author": "Your Name",
  "license": "MIT"

In this setup, CJS projects will default to the main entry point, while ESM projects will utilize the module entry. This approach guarantees that the library remains functional across different project configurations.

Leveraging the Exports Field for More Control

The exports field in package.json provides enhanced control over how different versions of your package are exposed. It allows you to define specific entry points for various conditions like requiring or importing the module:

  "exports": {
    ".": {
      "require": "./dist/index.cjs",
      "import": "./dist/index.mjs"

This configuration directs Node.js on how to handle the package whether it’s being required or imported, further refining module resolution and ensuring compatibility.

Integration Tips for Docker and DevOps Practices

Incorporating these practices into your CI/CD pipelines can significantly streamline deployments. As a Docker Captain, I recommend containerizing your development environments to match the configurations of your production environments closely. This ensures that your packages are tested and deployed in a consistent manner, reducing the chances of environment-specific bugs and enhancing the reliability of your deployment pipelines.


Adopting a dual-module strategy for your NPM packages not only broadens their applicability across various projects but also aligns with modern JavaScript development practices. By following these guidelines and integrating them with Docker-based workflows, you can enhance your project’s modularity and deployment efficiency.

Stay tuned for more insights on leveraging Docker and DevOps methodologies to refine your development and operational strategies!

My Courses

🎓 Dive into my comprehensive IT courses designed for enthusiasts and professionals alike. Whether you’re looking to master Docker, conquer Kubernetes, or advance your DevOps skills, my courses provide a structured pathway to enhancing your technical prowess.

My Services

💼 Take a look at my service catalog and find out how we can make your technological life better. Whether it’s increasing the efficiency of your IT infrastructure, advancing your career, or expanding your technological horizons — I’m here to help you achieve your goals. From DevOps transformations to building gaming computers — let’s make your technology unparalleled!

Refill My Coffee Supplies

💖 PayPal
🏆 Patreon
💎 GitHub
🥤 BuyMeaCoffee
🍪 Ko-fi

Follow Me

🎬 YouTube
🐦 Twitter
🎨 Instagram
🐘 Mastodon
🧵 Threads
🎸 Facebook
🧊 Bluesky
🎥 TikTok
🐈 GitHub

Is this content AI-generated?

Nope! Each article is crafted by me, fueled by a deep passion for Docker and decades of IT expertise. While I employ AI to refine the grammar—ensuring the technical details are conveyed clearly—the insights, strategies, and guidance are purely my own. This approach may occasionally activate AI detectors, but you can be certain that the underlying knowledge and experiences are authentically mine.

Vladimir Mikhalev
I’m Vladimir Mikhalev, the Docker Captain, but my friends can call me Valdemar.

DevOps Community

hey 👋 If you have questions about installation or configuration, then ask me and members of our community: