Tampermonkey can't get the value of the input box element input?

goal:
1. Plan to log in to some sites automatically, such as Baidu, Taobao
2, account password and other information can not be written in the script, use the function of chrome to fill out the form automatically

problem:
1, document.getElementById ("xxx") .value and other syntax is invalid
2. The value of the input box cannot be obtained in the code, but the value can be obtained in chrome console
3. It is suspected that it is a permission problem, but the get has not reached the point

.

google, baidu for several weeks, failed to solve the problem

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May.23,2022
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-64f5-1b3547c-4d61c.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3547c-4d61c.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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