How to remove all options from a list box using javascript?

 function clearListBox(listboxID)
 {
  // returns 1 if all items are sucessfully removed
  // otherwise returns zero.
  var mylistbox = document.getElementById(listboxID);
  if(mylistbox == null)
   return 1;
  while(mylistbox.length > 0)
  {
   mylistbox.remove(0);
  }
  return 1;
 }