function setDefaultEVC(object, defaultValue){
  if(object.value == defaultValue) object.value = "";
  return;
}

/** e-mail control
 *@param email - input element
 *param alert_msg - alerting message
 */
function kontrola_emailu(email, alert_msg){
  if(window.RegExp){
    maska = new RegExp("^[^.]+(\.[^.]+)*@([^.]+[.])+[a-z]{2,3}$");
    if(email){
      if (!maska.test(email.value)){
        window.alert(alert_msg);
        email.focus();
        return false;
      }else return true;
    }else return true;
  }else return true;
}

function hideGeneralDiv(id){
  var e = document.getElementById(id);
  if(e) e.style.display = 'none';
  return;
}

function showGeneralDiv(id){
  var e = document.getElementById(id);
  if(e) e.style.display = 'block';
  return;
}

function goToAnchor(name){
  var url = document.location.href;
  if(url.indexOf('#' + name) == -1){
    url += '#' + name;
  }
  document.location.href = url;

}

function changeLupa(id, mod, lupa){
  var elem = document.getElementById(id);
  if(elem){
    if(mod) elem.src = "pics/web/lupa2_over.png";
    else elem.src = "pics/web/" + lupa;
  }
  return;
}

function seradVypis(sel, url, page){
  var value = sel.options[sel.selectedIndex].value;
  if(value != 0) location.href = url + '?razeni=' + value + '&page=' + page;
  return;
}

function check_checkbox(id, mod){
  var ch = document.getElementById(id);
  switch(mod){
    case 0:  if(ch) ch.checked = !ch.checked; break; //invert value
    case 1:  if(ch) ch.checked = true; break; // checked always
    case 2:  if(ch) ch.checked = false; break; // unchecked always
    default :  if(ch) ch.checked = !ch.checked;
  }
  return;
}