Forms & Validation Interview Questions

Ionic supports multiple form types: 1) Template-driven forms for simple scenarios, 2) Reactive forms for complex validation, 3) Dynamic forms for runtime form generation, 4) Multi-step forms for complex workflows, 5) Nested forms for complex data structures, and 6) Custom form controls for specific needs. Each type has specific use cases based on form complexity and requirements.

Custom validator implementation includes: 1) Creating validator functions, 2) Implementing async validators, 3) Cross-field validation logic, 4) Custom error messages, 5) Validation timing control, and 6) Error state management. Important considerations include validation performance and reusability.

Form error handling best practices include: 1) Clear error message display, 2) Field-level error indication, 3) Form-level error summary, 4) Real-time validation feedback, 5) Error state persistence, and 6) Accessibility considerations for error messages. Consider implementing progressive error display.

Multi-step form implementation includes: 1) Step navigation logic, 2) Form state management, 3) Step validation rules, 4) Progress tracking, 5) Data persistence between steps, and 6) Step completion indicators. Consider implementing step-specific validation and data saving.

Form persistence strategies include: 1) Auto-save implementation, 2) Draft saving functionality, 3) Form state recovery, 4) Local storage utilization, 5) Sync with backend servers, and 6) Data version control. Consider implementing conflict resolution for concurrent edits.

Dynamic form generation involves: 1) Form configuration schema, 2) Control type mapping, 3) Validation rule generation, 4) Dynamic control updates, 5) Form layout management, and 6) State initialization logic. Consider implementing form template caching.

Common validation patterns include: 1) Required field validation, 2) Pattern matching rules, 3) Range validation, 4) Custom format validation, 5) Conditional validation rules, and 6) Cross-field validation. Consider implementing reusable validation functions.

Form submission handling includes: 1) Data validation before submit, 2) Loading state management, 3) Error handling strategy, 4) Success feedback display, 5) Form reset logic, and 6) Retry mechanism for failures. Consider implementing progressive form submission.

Form accessibility approaches include: 1) ARIA label implementation, 2) Keyboard navigation support, 3) Error announcement, 4) Focus management, 5) Screen reader compatibility, and 6) High contrast support. Consider implementing accessibility testing.

Performance optimization strategies include: 1) Debounce validation, 2) Lazy loading form sections, 3) Efficient change detection, 4) Memory management, 5) Event handling optimization, and 6) DOM updates minimization. Consider implementing virtual scrolling for large forms.

Data transformation handling includes: 1) Input formatting rules, 2) Output data mapping, 3) Type conversion logic, 4) Data normalization, 5) Format validation, and 6) Transformation error handling. Consider implementing bidirectional transformations.

Form UI/UX best practices include: 1) Clear field labeling, 2) Intuitive layout design, 3) Responsive form behavior, 4) Consistent styling, 5) Progress indication, and 6) Mobile-friendly input types. Consider implementing form analytics tracking.

Form state management includes: 1) Form control state tracking, 2) Validation state management, 3) Dirty/Pristine state handling, 4) Touch/Untouched tracking, 5) Error state management, and 6) Submit state control. Consider implementing state persistence.

Conditional field patterns include: 1) Dynamic field visibility, 2) Dependent validation rules, 3) Field state management, 4) Value dependency handling, 5) Layout adjustment logic, and 6) Performance optimization. Consider implementing field caching.