Function format

fmt/bytes.ts:118–167

(
  num: number,
  options: FormatOptions = {},
)

 * @throws {TypeError} If `num` is not a finite number.
 */
export function format(
  num: number,
  options: FormatOptions = {},
): string {
  if (!Number.isFinite(num)) {
    throw new TypeError(`Expected a finite number, got ${typeof num}: ${num}`);
  }

  const UNITS_FIRSTLETTER = (options.bits ? "b" : "B") + "kMGTPEZY";

  if (options.signed && num === 0) {
    return ` 0 ${UNITS_FIRSTLETTER[0]}`;
  }

  const prefix = num < 0 ? "-" : (options.signed ? "+" : "");
  num = Math.abs(num);

  const localeOptions = getLocaleOptions(options);

  if (num < 1) {
    const numberString = toLocaleString(num, options.locale, localeOptions);
    return prefix + numberString + " " + UNITS_FIRSTLETTER[0];
  }

  const exponent = Math.min(
    Math.floor(
      options.binary ? Math.log(num) / Math.log(1024) : Math.log10(num) / 3,
    ),
    UNITS_FIRSTLETTER.length - 1,
  );
  num /= Math.pow(options.binary ? 1024 : 1000, exponent);

  if (!localeOptions) {
    num = Number(num.toPrecision(3));
  }

  const numberString = toLocaleString(
    num,
    options.locale,
    localeOptions,
  );

  let unit = UNITS_FIRSTLETTER[exponent];
  if (exponent > 0) {
    unit += options.binary ? "i" : "";
    unit += options.bits ? "bit" : "B";
  }

  return prefix + numberString + " " + unit;
}

function getLocaleOptions(
  { maximumFractionDigits, minimumFractionDigits }: FormatOptions,