Understanding controlled and uncontrolled components is essential for React form handling. Here's a complete guide.
Controlled Components
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Uncontrolled Components
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Controlled Form Example
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Uncontrolled Form Example
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When to Use Each
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File Inputs (Always Uncontrolled)
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Mixed Approach
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Select Elements
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Checkboxes and Radio Buttons
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Reset Patterns
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Best Practices
Controlled:
✓ Use for validation requirements
✓ Use for formatted inputs
✓ Use for conditional logic
✓ Easier to test
Uncontrolled:
✓ Use for file inputs
✓ Use for simple forms
✓ Use for third-party integration
✓ Better performance for many inputs
General:
✓ Don't mix value and defaultValue
✓ Use key to reset uncontrolled
✓ Consider form libraries for complex forms
✓ Be consistent within a form
Avoid:
✗ Switching between controlled/uncontrolled
✗ Setting value without onChange
✗ Using controlled for file inputs
✗ Over-engineering simple forms
Conclusion
Controlled components give React full control over form state, enabling real-time validation and formatting. Uncontrolled components let the DOM manage values, which is simpler for basic forms. Choose based on your needs: use controlled for validation and dynamic behavior, uncontrolled for simplicity. File inputs are always uncontrolled. Consider form libraries like React Hook Form for complex scenarios.