Hook a client party to a new message in chat

josef

Hello, I am looking for a hook on the client side for a new unread chat message - which leads to such a result:

I searched well in the source code and did not find ...
I checked for example:
https://github.com/NodeBB/NodeBB/blob/master/public/src/app.js
https://github.com/NodeBB/NodeBB/blob/master/public/src/client/chats.js
https://github.com/NodeBB/NodeBB/tree/master/public/src/client/chats
And I searched the whole project with a code editor for the words "Action: Chat" or "Event: Chat" and went through the results, but did not find anything suitable.
The goal is to do a certain action (play a sound using JS) when there is an unread message, as there is on all chat platforms, for example Skype, WhatsApp, and more.

<baris>