serve.mjs

// Zero-dependency static file server with HTTP Range support. Serves the demo
// locally for the static acts (②③④⑥); the public copy is on GitHub Pages.
//   node serve.mjs          # http://localhost:8088
//   PORT=9000 node serve.mjs
import http from 'node:http';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

const DIR = path.dirname(fileURLToPath(import.meta.url));
const PORT = Number(process.env.PORT || 8088);
const TYPES = { '.html':'text/html', '.js':'text/javascript', '.mjs':'text/javascript', '.json':'application/json',
  '.jsonld':'application/json', '.ndjson':'application/x-ndjson', '.dat':'application/octet-stream',
  '.hex':'text/plain', '.txt':'text/plain', '.map':'application/json', '.css':'text/css', '.wasm':'application/wasm' };

http.createServer((req, res) => {
  const name = decodeURIComponent(req.url.split('?')[0]).replace(/^\/+/, '') || 'index.html';
  const file = path.join(DIR, path.normalize(name));
  if (!file.startsWith(DIR) || !fs.existsSync(file) || fs.statSync(file).isDirectory()) { res.writeHead(404); return res.end('not found'); }
  const size = fs.statSync(file).size;
  const base = { 'Content-Type': TYPES[path.extname(file)] || 'application/octet-stream', 'Access-Control-Allow-Origin': '*', 'Accept-Ranges': 'bytes' };
  const range = req.headers.range;
  if (range) {
    const m = /bytes=(\d*)-(\d*)/.exec(range);
    const start = m[1] ? Number(m[1]) : 0, end = m[2] ? Number(m[2]) : size - 1;
    res.writeHead(206, { ...base, 'Content-Range': `bytes ${start}-${end}/${size}`, 'Content-Length': end - start + 1 });
    fs.createReadStream(file, { start, end }).pipe(res);
  } else {
    res.writeHead(200, { ...base, 'Content-Length': size });
    fs.createReadStream(file).pipe(res);
  }
}).listen(PORT, () => console.log(`serving ${DIR} on http://localhost:${PORT}`));