Unable to log socket id during disconnection in Node.js

Question

I am trying to log the socket id when a user logs out of a chat room. Currently the logger is saying 'transport close has left the chatroom' instead of logging the socket id.

I have been able to get it to log 'transport close' or 'undefined' but can't seem to get it to save the socket.id before the connection closes. What am I doing wrong?

io.on('connection', function(socket){
    var user_id = socket.id;
    io.emit('broadcast', `--${user_id} has joined the chat room`);
    console.log(`[${user_id}] has joined the chat room`);
socket.on('chat message', function(msg){
    io.emit('chat message', `[${user_id}] ${msg}`);
    console.log(`[${user_id}] ${msg}`);
});
socket.on('disconnect', function(user_id){
    io.emit('broadcast', `${user_id} has left the chat room`);
    console.log(`${user_id} has left the chat room`);
    })
});

Answer 1

Use socket.id instead of user_id. Your callback function(user_id) is incorrect.

socket.on('disconnect', function(){
       io.emit('broadcast', socket.id + ' has left the chat room');
       console.log(socket.id + ' has left the chat room');
})