Vue project city selection page-brother component data transfer value (8-6)

Data transfer of sibling components

In fact, brothers pass on value from the son to the father, and then the father passes on to another son. Realize the brothers pass by value.

I want the English letters on the right to switch with those on the left.
The first one: Click the letter on the right and switch on the left.
The second one: slide the letters on the right, and follow the slide on the left.

1. Bound event
   
2. Outgoing events
   
3. Receive event
   
4. Invoke methods based on events
   
5. Return subcomponent
   
6. Receive data and listen
   

important point:

:ref $refs in vue How to access DOM elements in Vue