Question

I’m having a heck of a time finding documentation on io.sockets.clients() so I can retrieve the connected clients id, username, etc. When I alert(io.sockets.clients().length.toString()); it gives me the correct number, but I need to find the structure of the array. Is there a way I can figure out the array without knowing the structure? Much like php’s print_r()?

Code so far:

socket.on('switchRoom', function(newroom){
    var clients = io.sockets.clients();
    socket.emit('users', clients);
});

socket.on('users', function(usernames) {
    for(var client in usernames) {
        console.log(usernames[client].id + ' disconnected: ' +     usernames[client].disconnected)
    }
});

I receive this error after ‘switchRoom’ is fired

/home/ed/socket/chat/node_modules/socket.io/lib/parser.js:81
data = JSON.stringify(ev);
              ^
TypeError: Converting circular structure to JSON
at Object.stringify (native)
at Object.encodePacket (/home/ed/socket/chat/node_modules/socket.io/lib/parser.js:81:19)
at Socket.packet (/home/ed/socket/chat/node_modules/socket.io/lib/socket.js:202:21)
at Socket.emit (/home/ed/socket/chat/node_modules/socket.io/lib/socket.js:351:15)
at Socket.<anonymous> (/home/ed/socket/chat/app.js:58:10)
at Socket.$emit (events.js:64:17)
at SocketNamespace.handlePacket (/home/ed/socket/chat/node_modules/socket.io/lib/namespace.js:331:20)
at Manager.onClientMessage (/home/ed/socket/chat/node_modules/socket.io/lib/manager.js:436:38)
at WebSocket.onMessage (/home/ed/socket/chat/node_modules/socket.io/lib/transport.js:387:20)
at Parser.<anonymous> (/home/ed/socket/chat/node_modules/socket.io/lib/transports/websocket/hybi-07-12.js:38:10)

Answer 1

Are you doing this on the client side (in the browser) or on the server side? You mention using alert, but I’m not aware of a clients() method on the client side that does what you want.

On the server side, clients() returns an array of Sockets as defined by this method:

/**
 * Retrieves all clients as Socket instances as an array.
 *
 * @api public
 */

SocketNamespace.prototype.clients = function (room) {
  var room = this.name + (room !== undefined ?
     '/' + room : '');

  if (!this.manager.rooms[room]) {
    return [];
  }

  return this.manager.rooms[room].map(function (id) {
    return this.socket(id);
  }, this);
};

The Node.js console and browsers with dev tools provide a console object that allows debugging; generally, you can call console.log(something) where something pretty much anything; in the case of an object, the details of the object will be enumerated in one way or another.

[Edit]

Since you’re already using socket.set to store the username, perhaps you can try something like this:

// server

socket.on('connection', function(socket) {
  ...
  socket.on('disconnect', function() {
    socket.get('username', function (err, name) {
      socket.broadcast.emit('disconnected', name);
    });
  });
  ...
});

// client

socket.on('connect', function () {
  ...
  socket.on('disconnected', function(name) {
    console.log(name + " disconnected.");
  });
  ...
});