function nextpage(gotoURL){
  document.forms.compareForm.action = gotoURL;
  document.forms.compareForm.submit();
}

function add_checkprod (prod_id) {
  if (reachedMaxProd(document.compareForm.checklist.value)) {
    uncheckProd(prod_id);
    alert("You have already selected 5 products for comparision.");
  } else {
    document.compareForm.checklist.value = prod_id + '+' + document.compareForm.checklist.value;    
    document.filterForm.checklist.value = document.compareForm.checklist.value;
  } 
}

function rem_checkprod (prod_id) {
  document.compareForm.checklist.value = document.compareForm.checklist.value.replace(prod_id + '+','');
  document.filterForm.checklist.value = document.compareForm.checklist.value;
}

function reachedMaxProd(checkVal) {
  count = 0;
  sOcc = checkVal.indexOf("+");
  while (sOcc != -1) {
    count++;
    sOcc = checkVal.indexOf("+",sOcc+1); 
  }
  if (count >= 5) return true; 
  return false;
}

function uncheckProd(prod_id) {
  for (var i = 0; i < document.compareForm.elements.length; i++) {
    if (document.compareForm.elements[i].value == prod_id) {
      document.compareForm.elements[i].checked=false;
      break;
    }
  }
}