buffer-fetch.js

function bufferFetch(url) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    xhr.responseType = 'arraybuffer';
    xhr.onload = () => resolve(xhr.response); 
    xhr.onerror = () => reject(Error('Fetch failed'));
    xhr.open('GET', url);
    xhr.send();
  });
}