socket io rooms names and number of users inside specific room

I'm trying to build some basic chat (based with rooms) using socket.io versions: "socket.io": "^2.1.1" "socket.io-client": "^2.1.1"

I have a few basic questions that I couldn't find any working answers no matter how deep I looked for them.

1. When a user gets in a specific room I'm doing it (in the server) socket.join(roomName) so the room 'exists' only if there is at least on socket connected to this room ?

2. I want to create a screen with the rooms name and the number of the participates - (is it possible to get it by the client side socketIO's object ?), I found that it's possible to get the rooms names(server-side) by using io.sockets.adapter.rooms but I get really weird strings which are definitely not the room names.

3. I'm trying to create a page inside each room that shows the users that are connected to that room (connection that got into a room with socket.join(roomName))

I'm new to socket.io I hope someone can help me to understand better how to work with that, and what I'm missing in here.

thanks!

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