I get length 1 even It didn't connect to socket - node.js

Question

let app = require('express')(),
http = require('http').Server(app),
User = require('../models/users');
http.listen(8080, function () {
console.log('Socket IO server has been started on port 8080');
});
let io = require('socket.io')(http);
var socketRoom = {};
io.of('/chat').on('connection', function (socket) {
var ioRooms = io.of('/chat').adapter.rooms;
console.log(ioRooms) // I got length 1 when I print it.
socket.on('requestRandomChat', function (data) {
User.findOne({userToken : data.userToken}, function(err, user){
if(err) socket.emit('db error');
if(!user) socket.emit('db error : user not found');
else {
socket.emit('responseUserProfile', user);
for (var key in rooms){
if (key == ''){
continue;
}
if (rooms[key].length == 1){
var roomKey = key.replace('/', '');
socket.join(roomKey);
io.sockets.in(roomKey).emit('completeMatch', {});
socketRoom[socket.id] = roomKey;
return;
}
}
socket.join(user.userToken);
socketRoom[user.userToken] = socket.userToken;
}
});
});
socket.on('cancelRequest', function (data) {
socket.leave(socketRoom[socket.id]);
console.log(ioRooms);
});
socket.on('sendMessage', function (data) {
console.log(ioRooms);
console.log('sendMessage!');
io.of('/chat').in(socketRoom[socket.id]).emit('receiveMessage', data);
});
socket.on('disconnect', function (data) {
console.log(ioRooms);
var key = socketRoom[socket.id];
socket.leave(key);
io.of('/chat').in(key).emit('disconnect');
var clients = io.of('/chat').clients(key);
for (var i = 0; i < clients.length; i++) {
clients[i].leave(key);
}
});
});
when I trying to get a length of rooms, I get a length 1 with a socketId.
but I've never connected to the room. Is that default room? can somebody explain what's happening with the room socket?
//{ '/chat#2HAMaavywIwZ1B5fAAAD': Room { sockets: {
'/chat#2HAMaavywIwZ1B5fAAAD': true }, length: 1 } }

Answer 1

In socket io each socket is automatically connected to a default room identified by socket ID.
That's why you get length 1.
I hope you find it helpful.
http://socket.io/docs/rooms-and-namespaces/