var xb =
{
   evtHash: [],

   ieGetUniqueID: function(_elem)
   {
      if (_elem === window) { return 'theWindow'; }
      else if (_elem === document) { return 'theDocument'; }
      else { return _elem.uniqueID; }
   },

   addEvent: function(_elem, _evtName, _fn, _useCapture)
   {
      if (typeof _elem.addEventListener != 'undefined')
      { _elem.addEventListener(_evtName, _fn, _useCapture); }
      else if (typeof _elem.attachEvent != 'undefined')
      {
         var key = '{FNKEY::obj_' + xb.ieGetUniqueID(_elem) +
               '::evt_' + _evtName + '::fn_' + _fn + '}';
         var f = xb.evtHash[key];
         if (typeof f != 'undefined')
            { return; }

         f = function()
         {
            _fn.call(_elem);
         };

         xb.evtHash[key] = f;
         _elem.attachEvent('on' + _evtName, f);

         // attach unload event to the window to clean up possibly IE memory leaks
         window.attachEvent('onunload', function()
         {
            _elem.detachEvent('on' + _evtName, f);
         });

         key = null;
         //f = null;   /* DON'T null this out, or we won't be able to detach it */
      }
      else
         { _elem['on' + _evtName] = _fn; }
   },

   removeEvent: function(_elem, _evtName, _fn, _useCapture)
   {
      if (typeof _elem.removeEventListener != 'undefined')
         { _elem.removeEventListener(_evtName, _fn, _useCapture); }
      else if (typeof _elem.detachEvent != 'undefined')
      {
         var key = '{FNKEY::obj_' + xb.ieGetUniqueID(_elem) +
               '::evt' + _evtName + '::fn_' + _fn + '}';
         var f = xb.evtHash[key];
         if (typeof f != 'undefined')
         {
            _elem.detachEvent('on' + _evtName, f);
            delete xb.evtHash[key];
         }

         key = null;
         //f = null;   /* DON'T null this out, or we won't be able to detach it */
      }
   }
};