Effective form validation improves UX and data quality. Here's how to implement it.
Basic Controlled Form
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Custom useForm Hook
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Schema Validation with Zod
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Real-Time Validation
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Field Components
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Multi-Step Form
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Form Array (Dynamic Fields)
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Best Practices
Validation Timing:
✓ Validate on blur for first interaction
✓ Validate on change after first error
✓ Debounce async validations
✓ Show errors only after touch
UX:
✓ Clear errors when user starts typing
✓ Use aria attributes for accessibility
✓ Show loading states for async validation
✓ Disable submit during submission
Performance:
✓ Memoize validation functions
✓ Use controlled inputs for complex logic
✓ Debounce real-time validation
✓ Avoid re-renders with proper state structure
Security:
✓ Validate on server too
✓ Sanitize inputs
✓ Protect against XSS
✓ Rate limit submissions
Conclusion
Form validation improves data quality and user experience. Use custom hooks for reusable logic, schema libraries for complex validation, and real-time feedback for better UX. Always validate on the server as well.