server-qs.js

var http = require('http');
var url = require('url');
var querystring = require('querystring');

http.createServer(function (request, response) {
    var pathname = url.parse(request.url).pathname;
    var qs = querystring.parse(url.parse(request.url).query);
    console.log('Received ' + pathname + ' request.');

    var routes = {
        '/': function(request, response) {
            response.writeHead(200, {'Content-Type':'text/plain'});
            response.write('Hello World');
            response.end();
        },
        '/abc': function(request, response) {
            var type = 'text/plain';
            var output = 'test';

            if (typeof qs.format !== 'undefined' && qs.format === 'json') {
                type = 'application/json';
                output = JSON.stringify({ data: 'test' });
            }

            response.writeHead(200, {'Content-Type': type});
            response.write(output);
            response.end();
        }
    };

    if (typeof routes[pathname] === 'function') {
        routes[pathname](request, response);
    } else {
        response.writeHead(404);
        response.write('404 not found');
        response.end();
    }

}).listen(3000);