function to_int(strString) {
   var strValidChars = "0123456789";
   var strChar;
   var blnResult = true;
   if (strString.length == 0) return 0;
   for (i = 0; i < strString.length && blnResult == true; i++) {
     strChar = strString.charAt(i);
     if (strValidChars.indexOf(strChar) == -1) {
        blnResult = false;
     }
   }
   if (blnResult) {
     return strString;
   } else {
     return 0;
   };
}

function to_float(strString) {
   var strValidChars = "0123456789.";
   var strChar;
   var blnResult = true;
   if (strString.length == 0) return 0;
   for (i = 0; i < strString.length && blnResult == true; i++) {
     strChar = strString.charAt(i);
     if (strValidChars.indexOf(strChar) == -1) {
        blnResult = false;
     }
   }
   if (blnResult) {
     return strString;
   } else {
     return 0;
   };
}

// изменение количества
function spec_change(id) {
  
  var input_field = $('item_' + id);
  var sum_element = $('sum_' + id);
  var price_element = $('price_' + id);
  var overall_sum_element = $('overall_sum');
  
  var count = to_int(input_field.value);
  var sum = to_float(sum_element.innerHTML);
  var price = to_float(price_element.innerHTML);  
  var overall_sum = to_float(overall_sum_element.innerHTML);

  overall_sum = overall_sum - sum;
  sum = count * price;
  overall_sum = overall_sum + sum;

  input_field.value = count;
  sum_element.innerHTML = sum;
  overall_sum_element.innerHTML = overall_sum;

  return false;

}

function spec_send() {
  document.forms.form.formaction.value = 'send';
  document.forms.form.submit();
}

function spec_save() {
  document.forms.form.formaction.value = 'save';
  document.forms.form.submit();
}

function spec_clear() {
  document.forms.form.formaction.value = 'clear';
  document.forms.form.submit();
}

function spec_download() {
  document.forms.form.formaction.value = 'download';
  document.forms.form.submit();
}

function spec_download_filtered() {
  document.forms.form.formaction.value = 'download_filtered';
  document.forms.form.submit();
}