Concise HTTP server

You should move all require(...) calls to the very beginning of your code, instead of running require on each place locally.

In its current form, you won't see require errors until your server runs and receives its first requests. This is unfortunate. You usually want a program to fail as early as possible if it clearly won't work.

Rule of Repair (TAOUP): Repair what you can — but when you must fail, fail noisily and as soon as possible.

I modified as follows, in addition to ensure require error possibility checking, structurally better I guess. Plus, I modified to full async where it should be.

var httpServer = function(dir)
{
  var fs = require('fs');
  var path = require("path");
  var url = require('url');

  var mimeTypes = {
    "html": "text/html",
    "js": "text/javascript",
    "css": "text/css",
    "jpeg": "image/jpeg",
    "jpg": "image/jpeg",
    "png": "image/png",
    "gif": "image/gif",
    "svg": "image/svg"
    // more
  };

  var component = require('http')
    .createServer(function(req, res)
    {
      var uri = url.parse(req.url).pathname;
      var filepath = path.join(dir, unescape(uri));
      var indexfilepath = path.join(dir, unescape('index.html'));

      console.info('filepath', filepath);

      var f = function(err, stats)
      {
        if (stats === undefined) // path does not exit 404
        {
          res.writeHead(404,
          {
            'Content-Type': 'text/plain'
          });
          res.write('404 Not Found\n');
          res.end();

          return;
        }
        else if (stats.isFile()) // path exists, is a file
        {
          var mimeType = mimeTypes[path.extname(filepath).split(".")[1]];
          res
            .writeHead(200,
            {
              'Content-Type': mimeType
            });

          var fileStream =
            fs
            .createReadStream(filepath)
            .pipe(res);

          return;
        }
        else if (stats.isDirectory()) // path exists, is a directory
        {
          res
            .writeHead(200,
            {
              'Content-Type': "text/html"
            });
          var fileStream =
            fs
            .createReadStream(indexfilepath)
            .pipe(res);

          return;
        }
        else
        {
          // Symbolic link, other?
          // TODO: follow symlinks?  security?
          res
            .writeHead(500,
            {
              'Content-Type': 'text/plain'
            })
            .write('500 Internal server error\n')
            .end();

          return;
        }
      };

      fs.stat(filepath, f);

    });

  return component;
};


var port = 9999;
var dir = 'www';
var HTTPserver =
  httpServer(require('path')
    .join(__dirname, dir))
  .listen(port, function()
  {
    console.info('HTTP listening', port);
  });

simpler

var port = 9999;
var directory = 'www';

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

var mimeTypes = {
  "html": "text/html",
  "js": "text/javascript",
  "css": "text/css",
  "jpeg": "image/jpeg",
  "jpg": "image/jpeg",
  "png": "image/png",
  "gif": "image/gif",
  "svg": "image/svg"
    // more
};

var request = function(req, res)
{
  var uri = url.parse(req.url).pathname;
  var dir = path.join(__dirname, directory);
  var filepath = path.join(dir, unescape(uri));
  var indexfilepath = path.join(dir, unescape('index.html'));

  console.info('filepath', filepath);

  var f = function(err, stats)
  {
    if (stats === undefined) // path does not exit 404
    {
      res.writeHead(404,
      {
        'Content-Type': 'text/plain'
      });
      res.write('404 Not Found\n');
      res.end();

      return;
    }
    else if (stats.isFile()) // path exists, is a file
    {
      var mimeType = mimeTypes[path.extname(filepath).split(".")[1]];
      res
        .writeHead(200,
        {
          'Content-Type': mimeType
        });

      var fileStream =
        fs
        .createReadStream(filepath)
        .pipe(res);

      return;
    }
    else if (stats.isDirectory()) // path exists, is a directory
    {
      res
        .writeHead(200,
        {
          'Content-Type': "text/html"
        });

      var fileStream =
        fs
        .createReadStream(indexfilepath)
        .pipe(res);

      return;
    }
    else
    {
      // Symbolic link, other?
      // TODO: follow symlinks?  security?
      res
        .writeHead(500,
        {
          'Content-Type': 'text/plain'
        })
        .write('500 Internal server error\n')
        .end();

      return;
    }
  };

  fs.stat(filepath, f);
  return;
};

var serverUp = function()
{
  console.info('HTTP server listening', port);
  return;
};

var component = http
  .createServer(request)
  .listen(port, serverUp);