Function parseDateTimeSkeleton

packages/icu-skeleton-parser/date-time.ts:15–144

(
  skeleton: string
)

 * @param skeleton skeleton string
 */
export function parseDateTimeSkeleton(
  skeleton: string
): Intl.DateTimeFormatOptions {
  const result: Intl.DateTimeFormatOptions = {}
  skeleton.replace(DATE_TIME_REGEX, match => {
    const len = match.length
    switch (match[0]) {
      // Era
      case 'G':
        result.era = len === 4 ? 'long' : len === 5 ? 'narrow' : 'short'
        break
      // Year
      case 'y':
        result.year = len === 2 ? '2-digit' : 'numeric'
        break
      case 'Y':
      case 'u':
      case 'U':
      case 'r':
        throw new RangeError(
          '`Y/u/U/r` (year) patterns are not supported, use `y` instead'
        )
      // Quarter
      case 'q':
      case 'Q':
        throw new RangeError('`q/Q` (quarter) patterns are not supported')
      // Month
      case 'M':
      case 'L':
        result.month = ['numeric', '2-digit', 'short', 'long', 'narrow'][
          len - 1
        ] as 'numeric'
        break
      // Week
      case 'w':
      case 'W':
        throw new RangeError('`w/W` (week) patterns are not supported')
      case 'd':
        result.day = ['numeric', '2-digit'][len - 1] as 'numeric'
        break
      case 'D':
      case 'F':
      case 'g':
        throw new RangeError(
          '`D/F/g` (day) patterns are not supported, use `d` instead'
        )
      // Weekday
      case 'E':
        result.weekday = len === 4 ? 'long' : len === 5 ? 'narrow' : 'short'
        break
      case 'e':
        if (len < 4) {
          throw new RangeError('`e..eee` (weekday) patterns are not supported')
        }
        result.weekday = ['short', 'long', 'narrow', 'short'][
          len - 4
        ] as 'short'
        break