How would you implement HTTP response streaming in Node.js to begin sending data to a client before the entire response is ready, such as for a large report?

Rather than building a complete response in memory before calling res.end() once, you can call res.write() multiple times as data becomes progressively available, letting the client start receiving and processing data before the entire operation on the server side has finished -- particularly valuable for large exports or reports where waiting for the entire dataset to be assembled before sending anything would introduce significant unnecessary latency for the client.

app.get('/export', async (req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/csv', 'Transfer-Encoding': 'chunked' });
  res.write('id,name,email\n');
  for await (const batch of getRecordsInBatches()) {
    res.write(batch.map(r => `${r.id},${r.name},${r.email}\n`).join(''));
  }
  res.end();
});