function swapcod() {
  sel = document.getElementById('cod');
  tbl = document.getElementById('tblcod');
  if (sel.selectedIndex){
    tbl.className = 'codvisible';
    ar = document.getElementById('sa0');
    if (ar.checked){
      sameaddr(0);
    }
  } else {
    tbl.className = 'codhidden';
    sameaddr(1);
  }

}

function sameaddr(t){
  tbl = document.getElementById('tblbill');
  if (t == 0){
    tbl.className = 'codvisible';
  } else {
    tbl.className = 'codhidden';
  }
  console.log(t.value);
}