Modified version of https://stackoverflow.com/a/14919494/2803743

formatBytes.js

export default (bytes) => {
  const thresh = 1024;

  if (Math.abs(bytes) < thresh) {
    return bytes + ' B';
  }

  const units = ['kB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
  let u = -1;

  do {
    bytes /= thresh;
    ++u;
  } while (Math.abs(bytes) >= thresh && u < units.length - 1);

  return `${bytes.toFixed(1)} ${units[u]}`;
}