code: function _getModifiers() {
      var modifiers = '';
      if(_downKeys.length) {
        for(var i=_downKeys.length-1; i>=0; i--) {
          if(-1 !== _that.MODIFIERS.indexOf(_downKeys[i])) {
            modifiers += (modifiers ? ' ' : '') + _downKeys[i];
          }
        }
      }
      return modifiers;
    }
docs: Compute current modifiers