Understanding module systems is essential for TypeScript projects. Here's how they work and how to configure them.
Module Formats#
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tsconfig Module Options#
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ES Modules in Node.js#
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Import/Export Patterns#
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CommonJS Interoperability#
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Path Aliases#
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Barrel Files#
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Module Augmentation#
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Dual Package Publishing#
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Best Practices#
Configuration:
✓ Use "moduleResolution": "bundler" for apps
✓ Use "moduleResolution": "node16" for Node.js
✓ Enable esModuleInterop
✓ Use verbatimModuleSyntax
Imports:
✓ Use type-only imports when possible
✓ Prefer named exports over default
✓ Use path aliases consistently
✓ Avoid deep barrel re-exports
Publishing:
✓ Ship both ESM and CJS
✓ Include type definitions
✓ Use exports field properly
✓ Test in both module systems
Conclusion#
Understanding TypeScript's module systems helps you configure projects correctly and write interoperable code. Use ES Modules for modern projects, configure esModuleInterop for CommonJS compatibility, and set up proper dual-package exports when publishing libraries.