function showElement(id)
{
  var el = document.getElementById(id);
  if(el)
  {
      removeClass(el, "hidden");
  }
}

function hideElement(id)
{
    var el = document.getElementById(id);
    if(el)
    {
        addClass(el, "hidden");
    }
}

function addClass(el, cn)
{
  if(el)
  {
    if(el.className)
    {
      var str = el.className;
      if(str.indexOf(cn) == -1)
      {
        el.className = str + " " + cn;
      }
    }
    else
    {
      el.className = cn;
    }
  }
}
                                                                                                                                                          
function removeClass(el, cn)
{
  if(el && el.className)
  {
    var str = el.className;
    el.className = str.replace(cn, "");
  }
}

function addClassById(id, cn)
{
    var el = document.getElementById(id);
    addClass(el, cn);
}

function removeClassById(id, cn)
{
    var el = document.getElementById(id);
    removeClass(el, cn);
}

function swapElements(hideId, showId)
{
    hideElement(hideId);
    showElement(showId);
}

function swapClass(removeId, addId, cn)
{
    removeClassById(removeId, cn);
    addClassById(addId, cn);
}