A Simple NodeJS File Server with caching abilities

server.js

/*
 * Before executing this script
 *
 * 1. Create a dir named content
 * 2. With an index.html that requests for files e.g css
 *
 * This simple server will automatically fetch the 
 * requested resource from the content directory
 *
 * author: Evander Tino
 *
 */

var http = require('http');
var fs = require('fs');
var path = require('path');

var mimeTypes = {
  '.js' : 'text/javascript',
  '.html': 'text/html',
  '.css' : 'text/css'
};

var cache = {};

function cacheAndDeliver(f, cb) {
  fs.stat(f, function (err, stats) {
    if (err) {
      return console.log('Oh no!, Error', err);
    }
    var lastChanged = Date.parse(stats.ctime), 
	isUpdated = (cache[f]) && lastChanged > cache[f].timestamp;

    if (!cache[f] || isUpdated) {
      fs.readFile(f, function(err, data) {
        console.log('loading ' + f + ' from disk');
	if (!err) {
	  cache[f] = {content: data, timestamp: Date.now()};
	}
	cb(err, data);
      });
      return;
    }
    console.log('loading ' + f + ' from cache');
    cb(null, cache[f].content);
  });
}

http.createServer(function (request, response) {
  var lookup = path.basename(decodeURI(request.url)) || 'index.html';
  var f = 'content/' + lookup;
  fs.exists(f, function (exists) {
    if (exists) {
      cacheAndDeliver(f, function (err, data) {
	if (err) {
	  response.writeHead(500); 
	  response.end('Server Error!'); 
	  return; 
	}
	var headers = {'Content-Type': mimeTypes[path.extname(lookup)]};
	response.writeHead(200, headers);
	response.end(data);
      });
      return;
    }
    response.writeHead(404);
    response.end('Page Not Found');
  });
}).listen(8080);