JAVASCRIPT

is email js

/**
 * verifie si la chaine renseigné est un email
 * check if email is valide
 * @param string emailAdress
 * @return bool
 */
function isEmail(emailAdress){
    let regex = /^w+([.-]?w+)*@w+([.-]?w+)*(.w{2,3})+$/;

  if (emailAdress.match(regex)) 
    return true; 

   else 
    return false; 
}

//see https://regexr.com/3e48o for another exemple

Javascript validate email

function validateEmail($email) {
  var emailReg = /^([w-.]+@([w-]+.)+[w-]{2,4})?$/;
  return emailReg.test( $email );
}

if( !validateEmail(emailaddress)) { /* do stuff here */ }