When the mount method of vue takes no parameters?

new Vue ({.}). Mount (); does not add parameters here, but generally needs to add a dom selector. What is the operating mechanism when it is not added? can you analyze it from the source code level? Please give me more advice

Mar.20,2021

if $mount does not provide parameters, the template will be rendered as an element outside the document, and you must insert it into the document using native DOM API (original link: https://blog.csdn.net/c231115.)

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-64f5-1b30c9d-4d3df.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b30c9d-4d3df.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?