Node HTTP server

const path = require('path');
const http = require('http');
const fs = require('fs');
const arg = process.argv.at(2);
const cwd = process.cwd();
const webDir = arg ? path.isAbsolute(arg) ? arg : path.join(cwd, arg) : cwd;
const port = process.env.port || 8080;
const mimeTypeMap = {
    'bin': 'application/octet-stream',
    'css': 'text/css',
    'gif': 'image/gif',
    'htm': 'text/html',
    'html': 'text/html',
    'jpeg': 'image/jpeg',
    'jpg': 'image/jpeg',
    'js': 'application/javascript',
    'json': 'application/json',
    'png': 'image/png',
    'txt': 'text/plain',
};
const lookUpMimeType = (fileName) => {
    const extension = fileName.replace(/^.*\.(\w+)$/, '$1').toLowerCase();
    return mimeTypeMap[extension] ?? mimeTypeMap.bin;
};
const handleFileFetch = (req, res) => {
    const { url } = req;
    const urlPath = url.replace(/[?#].*/, '');
    const pathName = path.join(webDir, urlPath.replace(/\/$/, '/index.html'));
    if (!fs.existsSync(pathName)) {
        res.writeHead(404);
        res.end();
        return;
    }
    const stat = fs.lstatSync(pathName);
    if (stat.isDirectory()) {
        res.writeHead(303, { location: urlPath + '/' });
        res.end();
        return;
    }
    res.writeHead(200, {
        'content-type': lookUpMimeType(pathName),
        'content-length': stat.size,
    });
    const stream = fs.createReadStream(pathName);
    stream.on('data', (chunk) => res.write(chunk));
    stream.on('end', () => res.end());
    stream.on('error', error => {
        console.error(error);
        res.writeHead(500);
        res.end();
    });
};
const server = http.createServer((req, res) => {
    try {
        handleFileFetch(req, res);
    } catch(error) {
        console.error(error);
        res.writeHead(500);
        res.end();
    }
});
server.listen(port, () => {
    console.log('hosting', webDir);
    console.log(`http://localhost:${port} started`);
});