If you don't know either yet, I would suggest React.
React might be overkill for a very simple chat interface, but jQuery is steadily going out of fashion, and learning the basics of React is definitely going to pay off in the long term.
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
If you don't know either yet, I would suggest React.
React might be overkill for a very simple chat interface, but jQuery is steadily going out of fashion, and learning the basics of React is definitely going to pay off in the long term.