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.