LWCIntermediaterecord-edit-formvalidationforms
Troubleshoot lightning-record-edit-form custom validation timing
Real World Scenario
Custom onsubmit handler runs before field-level validation; invalid records reach Apex causing confusing duplicate error messages.
Expected Answer
• Use onload to register field change handlers for inline validation before submit
• reportValidity on native inputs; lightning-input-field exposes validity API
• Prevent default on submit when client validation fails
• Do not duplicate server validation messages — map Apex errors to fields
• Order: client required → format → custom cross-field → server
• Test required picklist and lookup validation paths separately
• Document validation ownership: LWC vs trigger vs validation rules
Follow-Up Questions & Answers
Click to expand — each follow-up includes a direct, interview-ready answer
Main difference: use case and scale. Use onload to register field change handlers for inline validation before submit. reportValidity on native inputs; lightning-input-field exposes validity API. Pick based on your integration pattern and team capability. Validation layering must be intentional — users hate seeing the same error three times in different wording. Balance speed of delivery with maintainability.
Architect Perspective
Validation layering must be intentional — users hate seeing the same error three times in different wording.