Format File Sizes in JavaScript

beautifulFilesize.js

const UNITS = ['byte', 'kilobyte', 'megabyte', 'gigabyte', 'terabyte', 'petabyte'];

function beautifulFilesize(filesizeBytes) {
  let unitIdx = 0;
  let magnitude = filesizeBytes;
  while (magnitude > 1000 && unitIdx < UNITS.length - 1) {
    unitIdx++;
    magnitude /= 1000.0;
  }
  const numberFmt = new Intl.NumberFormat('en', {
    maximumFractionDigits: unitIdx == 0 ? 0 : 2,
    minimumFractionDigits: unitIdx == 0 ? 0 : 2,
    style: 'unit',
    unit: UNITS[unitIdx],
    unitDisplay: 'short', // Options are "long" ("1.23 megabytes"), "short" ("1.23 MB"), and "narrow" ("1.23MB")
  });

  return numberFmt.format(magnitude);
}