Introduction
JavaScript has two main module systems: CommonJS (CJS) and ES Modules (ESM). Each has its strengths and ideal use cases.
Syntax
CommonJS uses require() and module.exports. ESM uses import and export. ESM syntax is static, enabling compile-time analysis.
Sync vs Async Loading
CommonJS loads modules synchronously, ideal for Node.js. ESM loads asynchronously, enabling tree shaking and better browser performance.
Compatibility
Node.js supports both since version 14. Use .mjs for ESM, .cjs for CommonJS, or set "type": "module" in package.json.
Performance
ESM enables tree shaking, async loading, and better caching. CommonJS is more mature and compatible with more libraries, especially older ones.
Migration
You can use both in the same project with interoperability. import() from CommonJS and createRequire from ESM allow coexistence.
Conclusion
ESM is the future, but CommonJS remains relevant. At Vynta, we use ESM in new projects and CommonJS when working with legacy libraries.