Transient Blog Post - http://theconnman.com/technical/2016/01/03/Transient.html

app.js

...

io.on('connection', function(socket) {
	socket.on('username', function(username) {
		socket.username = username;
	});
	socket.on('message', function(text) {
		rooms.send(io, socket, text, 'message');
	});
	socket.on('change', function(room) {
		if (socket.room) {
			rooms.leave(io, socket);
		}
		rooms.join(io, socket, room);
	});
	socket.on('leave', function() {
		if (socket.room) {
			rooms.leave(io, socket);
		}
	});
	socket.on('disconnect', function() {
		if (socket.username) {
			rooms.leave(io, socket);
		}
	});
});

...

public-js-app.js

...

socket.on('send:message', function(message) {
	$scope.messages.push(message);
});

...

$scope.sendMessage = function() {
	if ($scope.chat.message.length !== 0) {
		socket.emit('message', $scope.chat.message);
		$scope.chat.message = '';
		...
	}
};

...

rooms.js

...

rooms.send = function(io, socket, message, type) {
	io.to(socket.room).emit('send:message', {
		text: message,
		date: moment().format('HH:mm:ss'),
		type: type,
		user: socket.username
	});
};

rooms.leave = function(io, socket) {
	socket.leave(socket.room);
	rooms.send(io, socket, socket.username + ' left', 'join');
	console.log(socket.username + ' left ' + socket.room);
};

rooms.join = function(io, socket, room) {
	socket.room = room;
	socket.join(socket.room);
	rooms.send(io, socket, socket.username + ' joined', 'join');
	console.log(socket.username + ' joined ' + socket.room);
};

...