html check fields code example
Example: using javascript to validation email before next field
/^[a-zA-Z0–9.!#$%&’*+\/=?^_`{|}~-]+@[a-zA-Z0–9](?:[a-zA-Z0–9-]{0,61} [a-zA-Z0–9])?(?:\.[a-zA-Z0–9](?:[a-zA-Z0–9-]{0,61}[a-zA-Z0–9])?)*$/
/^[a-zA-Z0–9.!#$%&’*+\/=?^_`{|}~-]+@[a-zA-Z0–9](?:[a-zA-Z0–9-]{0,61} [a-zA-Z0–9])?(?:\.[a-zA-Z0–9](?:[a-zA-Z0–9-]{0,61}[a-zA-Z0–9])?)*$/