code: function(event) {
  				// Poor-man's hotkeys. See here for a complete implementation:
  				//   https://github.com/jeresig/jquery.hotkeys
  				var which = event.which,
  					et = event.type,
  					s = [];
  
  				if (event.altKey) {
  					s.push("alt");
  				}
  				if (event.ctrlKey) {
  					s.push("ctrl");
  				}
  				if (event.metaKey) {
  					s.push("meta");
  				}
  				if (event.shiftKey) {
  					s.push("shift");
  				}
  
  				if (et === "click" || et === "dblclick") {
  					s.push(MOUSE_BUTTONS[event.button] + et);
  				} else {
  					if (!IGNORE_KEYCODES[which]) {
  						s.push(
  							SPECIAL_KEYCODES[which] ||
  								String.fromCharCode(which).toLowerCase()
  						);
  					}
  				}
  				return s.join("+");
  			}
docs: Convert a keydown or mouse event to a canonical string like 'ctrl+a',
  'ctrl+shift+f2', 'shift+leftdblclick'.
  
  This is especially handy for switch-statements in event handlers.
  
  @param {event}
  @returns {string}
  
  @example
  
  switch( $.ui.fancytree.eventToString(event) ) {
  case "-":
  tree.nodeSetExpanded(ctx, false);
  break;
  case "shift+return":
  tree.nodeSetActive(ctx, true);
  break;
  case "down":
  res = node.navigate(event.which, activate);
  break;
  default:
  handled = false;
  }
  if( handled ){
  event.preventDefault();
  }