Express middleware provides powerful request processing. Here's how to use and create middleware effectively.
Middleware Basics
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Request Processing Chain
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Authentication Middleware
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Validation Middleware
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Error Handling Middleware
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Request Logging
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Caching Middleware
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Composition Patterns
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Best Practices
Organization:
✓ Keep middleware focused
✓ Use middleware factories
✓ Order middleware correctly
✓ Handle async errors
Performance:
✓ Keep middleware lightweight
✓ Cache when appropriate
✓ Avoid blocking operations
✓ Use streaming for large responses
Security:
✓ Validate all inputs
✓ Use helmet for headers
✓ Implement rate limiting
✓ Log security events
Conclusion
Express middleware enables clean, modular request processing. Use factories for configurable middleware, async handlers for error propagation, and proper ordering for correct execution. Well-designed middleware keeps route handlers focused on business logic.