serve.js

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

const root = __dirname;
const port = Number(process.env.PORT || 3000);
const host = '127.0.0.1';

const types = {
  '.html': 'text/html; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.md': 'text/markdown; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.svg': 'image/svg+xml',
  '.ico': 'image/x-icon'
};

function send(res, status, body, type = 'text/plain; charset=utf-8') {
  res.writeHead(status, { 'Content-Type': type });
  res.end(body);
}

const server = http.createServer((req, res) => {
  let urlPath = decodeURIComponent(req.url.split('?')[0]);
  if (urlPath === '/' || urlPath === '') {
    urlPath = '/index.html';
  }

  let filePath = path.normalize(path.join(root, urlPath));
  if (!filePath.startsWith(root)) {
    send(res, 403, 'Forbidden');
    return;
  }

  fs.stat(filePath, (statErr, stat) => {
    if (!statErr && stat.isDirectory()) {
      filePath = path.join(filePath, 'README.md');
    }

    fs.readFile(filePath, (readErr, data) => {
      if (readErr) {
        send(res, 404, 'Not found');
        return;
      }

      const type = types[path.extname(filePath).toLowerCase()] || 'application/octet-stream';
      send(res, 200, data, type);
    });
  });
});

server.listen(port, host, () => {
  console.log(`Docsify site is running at http://${host}:${port}`);
});