How to intelligently add a line to the beginning of a JavaScript block?

Question

JavaScript

Thank you very much in advance.
The page makes an ajax request to the server. After receiving the response, JavaScript processes it and generates a specific string that needs to be put at the beginning of the div block. This block also contains many blocks. What is the most reasonable way to do this, if this processed string is also some block?

Answer 1

So?
Or so
Tyk