Node.js server without a framework

This article provides a simple static file server built with pure Node.js without the use of a framework. The current state of Node.js is such that almost everything we needed is provided by the inbuilt APIs and just a few lines of code.

Example

A simple static file server built with Node.js:

import * as fs from 'node:fs';
import * as http from 'node:http';
import * as path from 'node:path';

const PORT = 8000;

const MIME_TYPES = {
  default: 'application/octet-stream',
  html: 'text/html; charset=UTF-8',
  js: 'application/javascript; charset=UTF-8',
  css: 'text/css',
  png: 'image/png',
  jpg: 'image/jpg',
  gif: 'image/gif',
  ico: 'image/x-icon',
  svg: 'image/svg+xml',
};

const STATIC_PATH = path.join(process.cwd(), './static');

const toBool = [() => true, () => false];

const prepareFile = async (url) => {
  const paths = [STATIC_PATH, url];
  if (url.endsWith('/')) paths.push('index.html');
  const filePath = path.join(...paths);
  const pathTraversal = !filePath.startsWith(STATIC_PATH);
  const exists = await fs.promises.access(filePath).then(...toBool);
  const found = !pathTraversal && exists;
  const streamPath = found ? filePath : STATIC_PATH + '/404.html';
  const ext = path.extname(streamPath).substring(1).toLowerCase();
  const stream = fs.createReadStream(streamPath);
  return { found, ext, stream };
};

http.createServer(async (req, res) => {
  const file = await prepareFile(req.url);
  const statusCode = file.found ? 200 : 404;
  const mimeType = MIME_TYPES[file.ext] || MIME_TYPES.default;
  res.writeHead(statusCode, { 'Content-Type': mimeType });
  file.stream.pipe(res);
  console.log(`${req.method} ${req.url} ${statusCode}`);
}).listen(PORT);

console.log(`Server running at http://127.0.0.1:${PORT}/`);

Breakdown

The following lines import internal Node.js modules.

import * as fs from 'node:fs';
import * as http from 'node:http';
import * as path from 'node:path';

Next we have a function for creating the server. https.createServer returns a Server object, which we can start up by listening on PORT.

http.createServer((req, res) => {
  /* handle http requests */
}).listen(PORT);

console.log(`Server running at http://127.0.0.1:${PORT}/`);

The asynchronous function prepareFile returns the structure: { found: boolean , ext: string, stream: ReadableStream }. If the file can be served (the server process has access and no path-traversal vulnerability is found), we will return the HTTP status of 200 as a statusCode indicating success (otherwise we return HTTP 404). Note that other status codes can be found in http.STATUS_CODES. With 404 status we will return content of '/404.html' file.

The extension of the file being requested will be parsed and lower-cased. After that we will search MIME_TYPES collection for the right MIME types. If no matches are found, we use the application/octet-stream as the default type.

Finally, if there are no errors, we send the requested file. The file.stream will contain a Readable stream that will be piped into res (an instance of the Writable stream).

res.writeHead(statusCode, { 'Content-Type': mimeType });
file.stream.pipe(res);