02-03.js

var http = require("http"),
  path = require("path"),
  fs = require("fs"),
  extensions = {
    ".html": "text/html",
    ".css": "text/css",
    ".js": "application/javascript",
    ".png": "image/png",
    ".gif": "image/gif",
    ".jpg": "image/jpeg"
  };
  
http.createServer(function(req, res) {
  var filename = path.basename(req.url) || "index.html",
    ext = path.extname(filename),
    dir = path.dirname(req.url).substring(1),
    localPath = __dirname + "/public/";

  if (extensions[ext]) {
    localPath += (dir ? dir + "/" : "") + filename;
    path.exists(localPath, function(exists) {
      if (exists) {
        getFile(localPath, extensions[ext], res);
      } else {
        res.writeHead(404);
        res.end();
      }
    });
  }
  
}).listen(8000);
      
function getFile(localPath, mimeType, res) {
  fs.readFile(localPath, function(err, contents) {
    if (!err) {
      res.writeHead(200, {
        "Content-Type": mimeType,
        "Content-Length": contents.length
      });
      res.end(contents);
    } else {
      res.writeHead(500);
      res.end();
    }
  });
}