Node.js chat client

This is a chat using Node.js, socket.io and MongoDB for storage.

I'd appreciate any feedback on what can be improved. I understand that this allows for non-unique usernames to be used, and it's currently a JavaScript prompt, however this is simply a demonstration for entering a username to test the functionality.

index.html

    
        Chat
        
    
    

        
            
            
        

        
        

            (function() {
                var socket = io.connect('http://127.0.0.1:8080'),
                    name = prompt('Enter your name');

                // Listen for output from server
                socket.on('output', function(data) {
                    var messages = document.querySelector('.chat .chat-messages');

                    if(data.length) {

                        // Loop results
                        for(var x = 0; x 

    

server.js

var mongo = require('mongodb').MongoClient,
    client = require('socket.io').listen(8080).sockets;

client.on('connection', function(socket) {

    // Connect to MongoDB
    mongo.connect('mongodb://127.0.0.1/chat', function(err, db) {
        if(err) throw err;

        var col = db.collection('messages');

        // Emit all messages
        col.find().limit(100).sort({_id: 1}).toArray(function(err, res) {
            if(err) throw err;
            socket.emit('output', res);
        });

        // Wait for input
        socket.on('input', function(data) {
            col.insert({name: data.name, message: data.message}, function(err, docs) {

                // Emit latest message to all clients
                client.emit('output', [data]);
            });
        });
    });

});

main.css (not as important here)

```
body,
textarea {
font: 13px "Trebuchet MS", sans-serif;
}

.chat {
max-width:300px;
}

.chat-messages,
.chat textarea {
border:1px solid #bbb;
}

.chat-messages {
width:100%;
height:300px;
overflow-y:scroll;
paddin

You should only open one connection to mongodb. Otherwise if you have 10 users connected on your chat, you'll have 10 opened connections to mongodb.

var mongo = require('mongodb').MongoClient;
var sio = require('socket.io');

mongo.connect('mongodb://127.0.0.1/chat', function(err, db) {
  if(err) throw err;

  var messages = db.collection('messages');

  client = sio.listen(8080).sockets;
  client.on('connection', function(socket) {
    messages.find().limit(100).sort({_id: 1}).toArray(function(err, res) {
      if(err) throw err;

      socket.emit('output', res);
    });

    socket.on('input', function(data) {
      messages.insert({name: data.name, message: data.message}, function(err, docs) {
        client.emit('output', [data]);
      });
    });
  });
});

From there, I would split the code into small functions. One could be call onInputMessage and looks something like.

var onInputMessage = function(data) {
  message.insert({name: data.name, message: data.message}, function(err, docs) {
    client.emit('output', [data]);
};

So that you can call it like this socket.on('input', onInputMessage);

StackExchange Code Review Q#40050, answer score: 3