Overview
Form Validation ensures user input meets requirements before submission. Shows clear error messages for invalid data.
How Validation Works
- Fill out the form
- Click Submit
- If errors exist, they are highlighted in red
- Error messages appear below the field
- Fix the errors and submit again
Common Validation Types
- Required: Field cannot be empty
- Email: Must be valid email format (user@example.com)
- Min Length: Must be at least X characters
- Max Length: Must be no more than X characters
- Number: Must be a number
- Min: Must be at least X (for numbers)
- Max: Must be no more than X (for numbers)
- Pattern: Must match a specific format (regex)
How to Fix Common Errors
Required Field Error
Message: "This field is required"
- Fill in the empty field
Invalid Email Error
Message: "Please enter a valid email address"
- Make sure email has @ and a domain (e.g., @gmail.com)
- Example of valid: user@example.com
Minimum Length Error
Message: "Must be at least 8 characters"
- Type more characters until requirement is met
Number Range Error
Message: "Must be between 1 and 100"
- Enter a number within the allowed range
Real-Time Validation
Some forms validate as you type:
- Green checkmark: Field is valid
- Red X or message: Field is invalid
- Fix errors before moving to next field
Quick Reference
| Error Type | How to Fix |
|---|---|
| Required | Fill in the field |
| Enter valid email format | |
| Min length | Type more characters |
| Max length | Type fewer characters |
| Number range | Enter number within range |