How to get username from a message?

Question

JavaScript

Hello.
I decided to make myself a bot for my group with the usual functionality /ban /warn /kick, etc.
But the question arose:
The administrator writes the command "/warn @username", how can I get exactly '@username', which is in this message, so that later I can get the id from it and manipulate it.
I understand that you need to get the message "ctx.message.text", it displays the text itself, I display it (screenshot), and then how to get the username?

Thanks in advance to everyone who answers