socket io broadcast to room

socket.to(room).broadcast.emit('hi')socket.to(room).broadcast.emit('hi')io.on('connection', function(socket){  socket.to('some room').emit('some event');});io.on('connection', socket => {  socket.on('disconnecting', () => {    const rooms = Object.keys(socket.rooms);    // the rooms array contains at least the socket ID  });  socket.on('disconnect', () => {    // socket.rooms === {}  });});