Drop-down Menu

[ File Path: super/select_menu.html ]

Press Ctrl key to select multiple cities
city: select

Explanation of implementation method
- Achieve this drop-down menu, it is relatively easy, you only need to control zTree Hide / Show, and location.
- Use zTree v3.x, you can select multiple nodes, so the multi-selection is also easy.
- Use the configuration parameters setting, fully meet the needs of most of the functionality.