function isblank(s)
{
  for(var i = 0; i < s.length; i++ )
  {
    var c = s.charAt(i);
    if((c!=' ') && (c!='\n') && (c!='\t')) 
      return false;
  }
  return true;
} // isblank
 
function getLanguage(f)
{
  var sLanguage = 'nl'
  var e = f.elements['lang'];
  if(e)
    sLanguage = e.value;

  return sLanguage;
}

function isMandatory(name)
{
  switch(name)
  {
    case 'Voorletters':
    case 'Voorvoegsel':
    case 'Achternaam':
    case 'Adres':
    case 'AdresNummer':
    case 'Postcode':
    case 'Woonplaats':
    case 'Telefoon':
    case 'EmailAdres':
      return true;
  }
    
  return false;
} // isMandatory

function verify(f)
{
  var msg;
  var no_auth = "";
  var empty_fields = "";
  var not_specified = "";
  var arItems = new Array();
  var iItems = 0;
  var prvElement = null;

  var sLanguage = getLanguage(f);

  for(var i=0;i<f.length;i++)
  {
    if(i>0)
      prvElement = f.elements[i-1];
    var e = f.elements[i];

    if(isMandatory(e.name))
    {
      switch(e.type.toLowerCase())
      {
        case 'text':
        case 'textarea':
        case 'password':
        case 'file':
          if(e.value == null || e.value == "" || isblank(e.value))
          {
            var prvStatus = prvElement?!prvElement.checked:true;
            if(prvStatus)
            {
              if(iItems>0)
                {
                var oe = arItems[iItems-1];
                if(oe.name != e.name)
                {
                  arItems.push(e);
                  iItems++;
                }
              }
              else
              {
                arItems.push(e);
                iItems++;
              }
            }
          }
          break;
        case 'radio':
          var prvStatus = false;
          if(prvElement)
          {
            if(prvElement.name == e.name)
            {
              prvStatus = !prvElement.checked;
            }
          }
          if(prvStatus && !e.checked)
          {
            if(iItems>0)
            {
              var oe = arItems[iItems-1];
              if(oe.name != e.name)
              {
                arItems.push(e);
                iItems++;
              }
            }
            else
            {
              arItems.push(e);
              iItems++;
            }
          }
          break;
      }
    }
  } // for all form-elements
 
  if(iItems>0)
  { 
    if(sLanguage == 'de')
    {
      msg = "----------------------------------------------------------------------------\n";
      msg += "Das Formular konnte nicht verschickt werden da die folgenden Angaben fehlen.\n";
      msg += "----------------------------------------------------------------------------\n";
    }
    else
    {
      msg = "--------------------------------------------------------------------\n";
      msg += "Het formulier is niet verstuurd door de volgende ontbrekende velden.\n";
      msg += "--------------------------------------------------------------------\n\n";
    }
 
    for(i=0;i<iItems;i++)
    {
      var e = arItems[i];
      msg += "\n         " + (e.attrname?e.attrname:e.name);
    }

    alert(msg);
    return false;
  }
  return true;
} // verify