How input of document-fragment uses JavaScript to write content

I don"t know how to start the title. < ("^") >
how can input, in document fragments created by document.createDocumentFragment modify the content in input through JavaScript?

if you modify it directly through the value property, the prompt "Please enter a user name" will appear and the contents of the input will not be recognized.

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-64f5-1b39c5a-2b939.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b39c5a-2b939.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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