Node.js chat frontend and server

chat-frontend.js

$(function () {
    "use strict";

    // for better performance - to avoid searching in DOM
    var content = $('#content');
    var input = $('#input');
    var status = $('#status');

    // my color assigned by the server
    var myColor = false;
    // my name sent to the server
    var myName = false;

    // if user is running mozilla then use it's built-in WebSocket
    window.WebSocket = window.WebSocket || window.MozWebSocket;

    // if browser doesn't support WebSocket, just show some notification and exit
    if (!window.WebSocket) {
        content.html($('<p>', { text: 'Sorry, but your browser doesn\'t '
                                    + 'support WebSockets.'} ));
        input.hide();
        $('span').hide();
        return;
    }

    // open connection
    var connection = new WebSocket('ws://127.0.0.1:1337');

    connection.onopen = function () {
        // first we want users to enter their names
        input.removeAttr('disabled');
        status.text('Choose name:');
    };

    connection.onerror = function (error) {
        // just in there were some problems with conenction...
        content.html($('<p>', { text: 'Sorry, but there\'s some problem with your '
                                    + 'connection or the server is down.</p>' } ));
    };

    // most important part - incoming messages
    connection.onmessage = function (message) {
        // try to parse JSON message. Because we know that the server always returns
        // JSON this should work without any problem but we should make sure that
        // the massage is not chunked or otherwise damaged.
        try {
            var json = JSON.parse(message.data);
        } catch (e) {
            console.log('This doesn\'t look like a valid JSON: ', message.data);
            return;
        }

        // NOTE: if you're not sure about the JSON structure
        // check the server source code above
        if (json.type === 'color') { // first response from the server with user's color
            myColor = json.data;
            status.text(myName + ': ').css('color', myColor);
            input.removeAttr('disabled').focus();
            // from now user can start sending messages
        } else if (json.type === 'history') { // entire message history
            // insert every single message to the chat window
            for (var i=0; i < json.data.length; i++) {
                addMessage(json.data[i].author, json.data[i].text,
                           json.data[i].color, new Date(json.data[i].time));
            }
        } else if (json.type === 'message') { // it's a single message
            input.removeAttr('disabled'); // let the user write another message
            addMessage(json.data.author, json.data.text,
                       json.data.color, new Date(json.data.time));
        } else {
            console.log('Hmm..., I\'ve never seen JSON like this: ', json);
        }
    };

    /**
     * Send mesage when user presses Enter key
     */
    input.keydown(function(e) {
        if (e.keyCode === 13) {
            var msg = $(this).val();
            if (!msg) {
                return;
            }
            // send the message as an ordinary text
            connection.send(msg);
            $(this).val('');
            // disable the input field to make the user wait until server
            // sends back response
            input.attr('disabled', 'disabled');

            // we know that the first message sent from a user their name
            if (myName === false) {
                myName = msg;
            }
        }
    });

    /**
     * This method is optional. If the server wasn't able to respond to the
     * in 3 seconds then show some error message to notify the user that
     * something is wrong.
     */
    setInterval(function() {
        if (connection.readyState !== 1) {
            status.text('Error');
            input.attr('disabled', 'disabled').val('Unable to comminucate '
                                                 + 'with the WebSocket server.');
        }
    }, 3000);

    /**
     * Add message to the chat window
     */
    function addMessage(author, message, color, dt) {
        content.append('<p><span style="color:' + color + '">' + author + '</span> @ ' +
             + (dt.getHours() < 10 ? '0' + dt.getHours() : dt.getHours()) + ':'
             + (dt.getMinutes() < 10 ? '0' + dt.getMinutes() : dt.getMinutes())
             + ': ' + message + '</p>');
    }
});

chat-server.js

// http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/
"use strict";

// Optional. You will see this name in eg. 'ps' or 'top' command
process.title = 'node-chat';

// Port where we'll run the websocket server
var webSocketsServerPort = 1337;

// websocket and http servers
var webSocketServer = require('websocket').server;
var http = require('http');

/**
 * Global variables
 */
// latest 100 messages
var history = [ ];
// list of currently connected clients (users)
var clients = [ ];

/**
 * Helper function for escaping input strings
 */
function htmlEntities(str) {
    return String(str).replace(/&/g, '&amp;').replace(/</g, '&lt;')
                      .replace(/>/g, '&gt;').replace(/"/g, '&quot;');
}

// Array with some colors
var colors = [ 'red', 'green', 'blue', 'magenta', 'purple', 'plum', 'orange' ];
// ... in random order
colors.sort(function(a,b) { return Math.random() > 0.5; } );

/**
 * HTTP server
 */
var server = http.createServer(function(request, response) {
    // Not important for us. We're writing WebSocket server, not HTTP server
});
server.listen(webSocketsServerPort, function() {
    console.log((new Date()) + " Server is listening on port " + webSocketsServerPort);
});

/**
 * WebSocket server
 */
var wsServer = new webSocketServer({
    // WebSocket server is tied to a HTTP server. To be honest I don't understand why.
    httpServer: server
});

// This callback function is called every time someone
// tries to connect to the WebSocket server
wsServer.on('request', function(request) {
    console.log((new Date()) + ' Connection from origin ' + request.origin + '.');

    // accept connection - you should check 'request.origin' to make sure that
    // client is connecting from your website
    // (http://en.wikipedia.org/wiki/Same_origin_policy)
    var connection = request.accept(null, request.origin); 
    // we need to know client index to remove them on 'close' event
    var index = clients.push(connection) - 1;
    var userName = false;
    var userColor = false;

    console.log((new Date()) + ' Connection accepted.');

    // send back chat history
    if (history.length > 0) {
        connection.sendUTF(JSON.stringify( { type: 'history', data: history} ));
    }

    // user sent some message
    connection.on('message', function(message) {
        if (message.type === 'utf8') { // accept only text
            if (userName === false) { // first message sent by user is their name
                // remember user name
                userName = htmlEntities(message.utf8Data);
                // get random color and send it back to the user
                userColor = colors.shift();
                connection.sendUTF(JSON.stringify({ type:'color', data: userColor }));
                console.log((new Date()) + ' User is known as: ' + userName
                            + ' with ' + userColor + ' color.');

            } else { // log and broadcast the message
                console.log((new Date()) + ' Received Message from '
                            + userName + ': ' + message.utf8Data);
                
                // we want to keep history of all sent messages
                var obj = {
                    time: (new Date()).getTime(),
                    text: htmlEntities(message.utf8Data),
                    author: userName,
                    color: userColor
                };
                history.push(obj);
                history = history.slice(-100);

                // broadcast message to all connected clients
                var json = JSON.stringify({ type:'message', data: obj });
                for (var i=0; i < clients.length; i++) {
                    clients[i].sendUTF(json);
                }
            }
        }
    });

    // user disconnected
    connection.on('close', function(connection) {
        if (userName !== false && userColor !== false) {
            console.log((new Date()) + " Peer "
                + connection.remoteAddress + " disconnected.");
            // remove user from the list of connected clients
            clients.splice(index, 1);
            // push back user's color to be reused by another user
            colors.push(userColor);
        }
    });

});

frontend.html

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>WebSockets - Simple chat</title>

        <style>
        * { font-family:tahoma; font-size:12px; padding:0px; margin:0px; }
        p { line-height:18px; }
        div { width:500px; margin-left:auto; margin-right:auto;}
        #content { padding:5px; background:#ddd; border-radius:5px;
                   border:1px solid #CCC; margin-top:10px; }
        #input { border-radius:2px; border:1px solid #ccc;
                 margin-top:10px; padding:5px; width:400px;  }
        #status { width:88px; display:block; float:left; margin-top:15px; }
        </style>
    </head>
    <body>
        <div id="content"></div>
        <div>
            <span id="status">Connecting...</span>
            <input type="text" id="input" disabled="disabled" />
        </div>

        <script src="//ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
        <script src="frontend.js"></script>
    </body>
</html>