Javascript in the thank you page is removed and/or not displayed correctly

Hello Villa Team,

I would like to insert a text field in the design editor or layout.
In the text field I would like to insert a button with Javascript to print an order receipt, but the link in the button in which Javascript is implemented is deleted.
For example:
From …
becomes: …
The inserted Javascript is also treated negatively.
How can I avoid that?
Thanks in advance.
Jürgen