format method

String format(String pattern)

Formats this date using a simple pattern.

Supported tokens: yyyy, yy, MM, M, dd, d, HH, H, mm, ss, EEE (weekday abbr), EEEE (weekday full), MMM (month abbr), MMMM (month full).

DateTime(2024, 3, 5).format('dd MMM yyyy') // '05 Mar 2024'

Implementation

String format(String pattern) {
  const weekdayAbbr = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'];
  const weekdayFull = [
    'Monday',
    'Tuesday',
    'Wednesday',
    'Thursday',
    'Friday',
    'Saturday',
    'Sunday',
  ];
  const monthAbbr = [
    'Jan',
    'Feb',
    'Mar',
    'Apr',
    'May',
    'Jun',
    'Jul',
    'Aug',
    'Sep',
    'Oct',
    'Nov',
    'Dec',
  ];
  const monthFull = [
    'January',
    'February',
    'March',
    'April',
    'May',
    'June',
    'July',
    'August',
    'September',
    'October',
    'November',
    'December',
  ];

  // Scan the pattern left-to-right, matching the longest token first.
  final tokenRe = RegExp(
    r'yyyy|yy|MMMM|MMM|MM|M|dd|d|HH|H|mm|ss|EEEE|EEE|.',
  );
  return pattern.replaceAllMapped(tokenRe, (m) {
    switch (m[0]) {
      case 'yyyy':
        return year.toString().padLeft(4, '0');
      case 'yy':
        return (year % 100).toString().padLeft(2, '0');
      case 'MMMM':
        return monthFull[month - 1];
      case 'MMM':
        return monthAbbr[month - 1];
      case 'MM':
        return month.toString().padLeft(2, '0');
      case 'M':
        return month.toString();
      case 'dd':
        return day.toString().padLeft(2, '0');
      case 'd':
        return day.toString();
      case 'HH':
        return hour.toString().padLeft(2, '0');
      case 'H':
        return hour.toString();
      case 'mm':
        return minute.toString().padLeft(2, '0');
      case 'ss':
        return second.toString().padLeft(2, '0');
      case 'EEEE':
        return weekdayFull[weekday - 1];
      case 'EEE':
        return weekdayAbbr[weekday - 1];
      default:
        return m[0]!;
    }
  });
}