function IsNumeric(sText)

{
   var ValidChars = "0123456789.";
   var IsNumber=true;
   var Char;


   for (i = 0; i < sText.length && IsNumber == true; i++)
      {
      Char = sText.charAt(i);
      if (ValidChars.indexOf(Char) == -1)
         {
         IsNumber = false;
         }
      }
   return IsNumber;

   }

function countTotalPrice(i){
    var count = document.getElementById('priceItemsCount').value;
    var discount = document.getElementById('discountVal').value;

    //value validation
    if(!IsNumeric(document.getElementById('priceItem' + i).value) || document.getElementById('priceItem' + i).value == '') document.getElementById('priceItem' + i).value = 0;

    var sum = 0;
    var sum2disc = 0;

    for(var j = 1; j <= count; j++){
        sum += document.getElementById('priceItem' + j).value * document.getElementById('price' + j).value;
        if(document.getElementById('rg' + j).value == 1) sum2disc += document.getElementById('priceItem' + j).value * document.getElementById('price' + j).value;
    }

    if(discount != 0 && document.getElementById('registered').value == 1){
        var disc = Math.round((discount / 100) * sum2disc) * -1;
        sum += disc;
        document.getElementById('priceDiscount').innerHTML = disc + ',- Kč';
    }

    document.getElementById('priceTotal').innerHTML = sum;

}

function regChange(checked){
    if(checked == true){
        document.getElementById('regBox').style.display = 'block';
        document.getElementById('discRow').style.visibility = 'visible';
        document.getElementById('registered').value = 1;
    }
    else {
        document.getElementById('regBox').style.display = 'none';
        document.getElementById('discRow').style.visibility = 'hidden';
        document.getElementById('registered').value = 0;
    }
    countTotalPrice(1);
}