function stripHTML(oldString) {

var re= /<\S[^>]*>/g; 
oldString = oldString.replace(re,""); 
return oldString;
  
}

function isEmailAddress (string) {
  var addressPattern = 
    /^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/;
  return addressPattern.test(string);
}
function checkEmail (field) {
  if (!isEmailAddress(field.value)) {
    alert('Prosím vložte správnu e-mailovú adresu!');
    field.focus();
    field.select();
  }
}