CompressionStream

const compressText = async (text, format = 'gzip') => {
  // Blob liefert einen Bytestrom, pipeThrough hängt die Kompression an
  const stream = new Blob([text]).stream()
    .pipeThrough(new CompressionStream(format));
  // Response sammelt den Stream bequem in einem ArrayBuffer
  const buffer = await new Response(stream).arrayBuffer();
  return new Uint8Array(buffer);
};

const json = JSON.stringify(Array.from({ length: 1000 }, (_, i) => ({ id: i, status: 'aktiv' })));
const gz = await compressText(json);

console.log(`Original: ${json.length} Bytes, gzip: ${gz.byteLength} Bytes`);
console.log(gz[0].toString(16), gz[1].toString(16)); // gzip-Magic-Bytes

// <input type="file" id="datei">
const input = document.querySelector('#datei');

input.addEventListener('change', async () => {
  const file = input.files[0];
  if (!file) return;

  const compressed = file.stream().pipeThrough(new CompressionStream('gzip'));
  const blob = await new Response(compressed).blob();

  const url = URL.createObjectURL(blob);
  const a = Object.assign(document.createElement('a'), {
    href: url,
    download: `${file.name}.gz`
  });
  a.click();
  URL.revokeObjectURL(url);
  console.log(`${file.size} → ${blob.size} Bytes`);
});

const text = 'Hallo Welt! '.repeat(500);

// Komprimieren
const packed = await new Response(
  new Blob([text]).stream().pipeThrough(new CompressionStream('deflate-raw'))
).arrayBuffer();

// Entpacken und direkt wieder als Text dekodieren
const unpacked = await new Response(
  new Blob([packed]).stream()
    .pipeThrough(new DecompressionStream('deflate-raw'))
    .pipeThrough(new TextDecoderStream())
).text();

console.log(packed.byteLength, unpacked === text);

const cs = new CompressionStream('gzip');
const writer = cs.writable.getWriter();

// Schreiben und Lesen laufen parallel, damit der Rückstau keinen Deadlock auslöst
const resultPromise = new Response(cs.readable).arrayBuffer();

const encoder = new TextEncoder();
for (const zeile of ['Zeile 1\n', 'Zeile 2\n', 'Zeile 3\n']) {
  await writer.write(encoder.encode(zeile));
}
await writer.close();

const result = await resultPromise;
console.log('Komprimiert:', result.byteLength, 'Bytes');