Core Validation Rules

Built-in rules

Core includes isRequired, isChecked, isNumber, isAboveMin, isBelowMax, range, regEx, regExLiteral, userDefined, isEmail, isDate, isZipCode, isPhone, isVin, and isSSN.

Optional behavior

Format rules are optional unless paired with isRequired.

helper.validateFor('email').isEmail('Invalid email');
helper.validateFor('requiredEmail')
  .isRequired('Email is required')
  .isEmail('Invalid email');

Rule order

Put required checks before format checks so summaries read naturally.

helper.validateFor('quantity')
  .isRequired('Quantity is required')
  .isNumber('Quantity must be numeric')
  .range('Quantity must be between 1 and 10', 1, 10, 'number');

Custom rules

helper.validateFor('code').userDefined('Code is unavailable', async (_model, value, message) => {
  const available = await checkCodeAvailability(String(value));
  return available ? true : { message };
});

Use explicit messages that tell the user how to recover.