server.js

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

const server = http.createServer((req, res) => {
  let filePath = '.' + req.url;
  if (filePath === './') {
    filePath = './index.html';
  }

  const extname = String(path.extname(filePath)).toLowerCase();
  const contentType = {
    '.html': 'text/html',
    '.css': 'text/css',
    '.js': 'text/javascript',
  }[extname] || 'application/octet-stream';

  fs.readFile(filePath, (err, content) => {
    if (err) {
      if (err.code === 'ENOENT') {
        res.writeHead(404);
        res.end('404 Not Found');
      } else {
        res.writeHead(500);
        res.end('500 Internal Server Error');
      }
    } else {
      res.writeHead(200, { 'Content-Type': contentType });
      res.end(content, 'utf-8');
    }
  });
});

const port = 3000;
server.listen(port, () => {
  console.log(`Server running at http://localhost:${port}/`);
});