Function formatISO

pkgs/core/src/formatISO/index.ts:46–107

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

 * //=> '19:00:52Z'
 */
export function formatISO(
  date: DateArg<Date> & {},
  options?: FormatISOOptions,
): string {
  const date_ = toDate(date, options?.in);

  if (isNaN(+date_)) {
    throw new RangeError("Invalid time value");
  }

  const format = options?.format ?? "extended";
  const representation = options?.representation ?? "complete";

  let result = "";
  let tzOffset = "";

  const dateDelimiter = format === "extended" ? "-" : "";
  const timeDelimiter = format === "extended" ? ":" : "";

  // Representation is either 'date' or 'complete'
  if (representation !== "time") {
    const day = addLeadingZeros(date_.getDate(), 2);
    const month = addLeadingZeros(date_.getMonth() + 1, 2);
    const year = addLeadingZeros(date_.getFullYear(), 4);

    // yyyyMMdd or yyyy-MM-dd.
    result = `${year}${dateDelimiter}${month}${dateDelimiter}${day}`;
  }

  // Representation is either 'time' or 'complete'
  if (representation !== "date") {
    // Add the timezone.
    const offset = date_.getTimezoneOffset();

    if (offset !== 0) {
      const absoluteOffset = Math.abs(offset);
      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 = offset < 0 ? "+" : "-";

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

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

    // If there's also date, separate it with time with 'T'
    const separator = result === "" ? "" : "T";

    // Creates a time string consisting of hour, minute, and second, separated by delimiters, if defined.
    const time = [hour, minute, second].join(timeDelimiter);

    // HHmmss or HH:mm:ss.
    result = `${result}${separator}${time}${tzOffset}`;