Function compareCaseFirst

packages/intl-collator/compare.ts:516–545

(
  left: string,
  right: string,
  locale: string,
  caseFirst: IntlCollatorInternal['caseFirst']
)

}

function compareCaseFirst(
  left: string,
  right: string,
  locale: string,
  caseFirst: IntlCollatorInternal['caseFirst']
): number {
  if (caseFirst === 'false') {
    return 0
  }
  const length = Math.min(left.length, right.length)
  for (let i = 0; i < length; i++) {
    const leftChar = left.charAt(i)
    const rightChar = right.charAt(i)
    const lowerLeft = leftChar.toLocaleLowerCase(locale)
    const lowerRight = rightChar.toLocaleLowerCase(locale)
    if (lowerLeft !== lowerRight) {
      continue
    }
    const leftIsUpper = leftChar !== lowerLeft
    const rightIsUpper = rightChar !== lowerRight
    if (leftIsUpper !== rightIsUpper) {
      // ECMA-402 caseFirst / Unicode extension kf determines whether upper or
      // lower case sorts first once base collation weights compare equal.
      // https://tc39.es/ecma402/#sec-initializecollator
      const upperResult = leftIsUpper ? -1 : 1
      return caseFirst === 'upper' ? upperResult : -upperResult
    }
  }
  return 0
}

export function compareCollatorStrings(
  slots: IntlCollatorInternal,