support_check_with_piping_server.html

<script>
const readableStream = new ReadableStream( {
  start(controller) {
    controller.enqueue(new Uint8Array([65, 66, 67]));
    controller.close();
  }
});

// (from: https://qiita.com/ryounagaoka/items/4736c225bdd86a74d59c)
const path = Math.random().toString(36).slice(-8);
const url = `https://ppng.io/${path}`;

fetch(url, {
  method: "POST",
  body: readableStream,
  allowHTTP1ForStreamingUpload: true,
});

(async () => {
  const res = await fetch(url);
  const text = await res.text()
  const readableStreamSupport = text === 'ABC';
  document.write(`support: ${readableStreamSupport}, text: ${text}`);
})();
</script>