prettier-plugin-imports/src/utils/natural-sort.ts

A prettier plugins to sort imports in provided RegEx order

export function naturalSort(a: string, b: string): number {
  const left = typeof a === 'string' ? a : String(a);
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Collator/Collator#syntax
  const sortOptions: Intl.CollatorOptions = {
    sensitivity: 'base',
    numeric: true,
    caseFirst: 'lower',
  };
  return left.localeCompare(b, 'en', sortOptions);
}

/**
 * Using a custom comparison function here, as `String.localeCompare` does not
 * support sorting characters with all uppercase letters before lowercase
 * letters, which is the desired behavior for a case-sensitive import sort. When
 * `sensitivity` is set to `base`, `String.localeCompare` sorts alphabetically
 * and then by case, but we want to sort by case first (then alphabetical).
 */
const numericRegex = /^\d+/;
export function naturalSortCaseSensitive(a: string, b: string) {
  let aIndex = 0;
  let bIndex = 0;
  while (aIndex < Math.max(a.length, b.length)) {
    // check if we've encountered a number and compare appropriately if so
    const aNumericMatch = a.slice(aIndex).match(numericRegex);
    const bNumericMatch = b.slice(bIndex).match(numericRegex);
    if (aNumericMatch && !bNumericMatch) return -1;
    if (!aNumericMatch && bNumericMatch) return 1;
    if (aNumericMatch && bNumericMatch) {
      const aNumber = parseInt(aNumericMatch[0]);
      const bNumber = parseInt(bNumericMatch[0]);
      if (aNumber > bNumber) return 1;
      if (aNumber < bNumber) return -1;
      aIndex += aNumericMatch[0].length;
      bIndex += bNumericMatch[0].length;
    }
    // otherwise just compare characters directly
    const aChar = a[aIndex];
    const bChar = b[bIndex];
    if (aChar && !bChar) return 1;
    if (!aChar && bChar) return -1;
    if (aChar !== bChar) return aChar.charCodeAt(0) - bChar.charCodeAt(0);
    aIndex++;
    bIndex++;
  }
  return 0;
}