Organizing Node.js code into reusable modules is fundamental for building maintainable applications, and understanding the module system is crucial for every Node.js developer. With 10 years of experience in Node.js development since 2014 and as the creator of CoreUI, I’ve built countless server-side applications and npm packages using module systems. From my expertise, CommonJS remains the traditional and widely-supported module format in Node.js, using require() to import and module.exports to export functionality. This approach is synchronous, battle-tested, and compatible with the vast majority of npm packages in the ecosystem.