// Toggles the elem to be shown or hidden (based on if currently hidden/shown).
var toggleHideUnhideElem = function(doc, elemId){
  var elem = doc.getElementById(elemId);
  var dsply = elem.style.display;
  if(dsply === 'none') { dsply = 'block'; } else { dsply = 'none'; }
  elem.style.display = dsply;
}