The code from the talk I gave today about Node.js

rest_calc.js

/*
 * Rest Calculator Server
 *
 * Based on "Building a Simple Web Service" screencast 
 * from thinkvitamin.com
 */

var util = require('util'),
    http = require('http');

var ops = {
    add : function(a, b) { return a + b },
    sub : function(a, b) { return a - b },
    mul : function(a, b) { return a * b },
    div : function(a, b) { return a / b },
};

function RestCalc (options) {
    this.settings = {
        port : options.port || 80
    };
    this.init();
};

RestCalc.prototype.init = function () {
    this.httpServer = this.createHTTPServer();
    this.httpServer.listen(this.settings.port);
    console.log('Server running at http://localhost:' + this.settings.port);
};

RestCalc.prototype.createHTTPServer = function (port) {

    var server = http.createServer(function (request, response) {

        var parts = request.url.split('/');

        var op = ops[parts[1]];
        var a  = parseInt(parts[2], 10);
        var b  = parseInt(parts[3], 10);

        var result = op ? op(a, b) : 'Invalid Request';

        response.writeHead(200, {'Content-Type' : 'text/html'});
        response.write('<p>' + result + '</p>');
        response.end();
    });

    return server;
};

module.exports = RestCalc;

server.js

/* Server Launcher */

require.paths.unshift(__dirname + '/lib');

var RestCalc = require('rest_calc');

new RestCalc({
    port : 8000
});