Function formatRFC3339

pkgs/core/src/formatRFC3339/index.ts:41–86

(
  date: DateArg<Date> & {},
  options?: FormatRFC3339Options,
)

 * //=> '2019-09-18T19:00:52.234Z'
 */
export function formatRFC3339(
  date: DateArg<Date> & {},
  options?: FormatRFC3339Options,
): string {
  const date_ = toDate(date, options?.in);

  if (!isValid(date_)) {
    throw new RangeError("Invalid time value");
  }

  const fractionDigits = options?.fractionDigits ?? 0;

  const day = addLeadingZeros(date_.getDate(), 2);
  const month = addLeadingZeros(date_.getMonth() + 1, 2);
  const year = date_.getFullYear();

  const hour = addLeadingZeros(date_.getHours(), 2);
  const minute = addLeadingZeros(date_.getMinutes(), 2);
  const second = addLeadingZeros(date_.getSeconds(), 2);

  let fractionalSecond = "";
  if (fractionDigits > 0) {
    const milliseconds = date_.getMilliseconds();
    const fractionalSeconds = Math.trunc(
      milliseconds * Math.pow(10, fractionDigits - 3),
    );
    fractionalSecond = "." + addLeadingZeros(fractionalSeconds, fractionDigits);
  }

  let offset = "";
  const tzOffset = date_.getTimezoneOffset();

  if (tzOffset !== 0) {
    const absoluteOffset = Math.abs(tzOffset);
    const hourOffset = addLeadingZeros(Math.trunc(absoluteOffset / 60), 2);
    const minuteOffset = addLeadingZeros(absoluteOffset % 60, 2);
    // If less than 0, the sign is +, because it is ahead of time.
    const sign = tzOffset < 0 ? "+" : "-";

    offset = `${sign}${hourOffset}:${minuteOffset}`;
  } else {
    offset = "Z";
  }

  return `${year}-${month}-${day}T${hour}:${minute}:${second}${fractionalSecond}${offset}`;
}