How the tree component in elementUI expands the first node by default when loading for the first time

elementUI
clipboard.png
is used in the project. How to implement the default deployment of the first level after the initial load?

Apr.02,2021

clipboard.png

look at the document

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1ea5773-1d58.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1ea5773-1d58.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?