Performs a natural sort based on two variables' string values.

nat-sort.js

/** 
 * Performs a natural sort based on two variables' string values.
 * Example:
 *     ['C12', 'B', 'c2', 'a', 'c1'].sort(natSort); //=> ['a', 'B', 'c1', 'c2', 'C12']
 *     
 *     [{name: 'Bob'}, {name: 'Zack'}, {name: 'Alex'}].sort(function(a, b) {
 *         return natSort(a, b, 'name', true);
 *     }); //=> [{name: 'Alex'}, {name: 'Bob'}, {name: 'Zack'}]
 * 
 * @param {any} a
 * @param {any} b
 * @param {string} [key]
 * @param {boolean} [reverse = false]
 * @return {number}
 */
export default function natSort(a, b, key, reverse = false) {
  /** @type {number} */
  let sign = reverse ? -1 : 1;
  if (key) {
    a = a[key];
    b = b[key];
  }
  /** @type {string} */
  let aStr = String(a);
  if (a.length === 0) return -sign;
  /** @type {string} */
  let bStr = String(b);
  if (b.length === 0) return sign;
  /** @type {number} */
  let i = 0;
  // Split a and b based on number and non-number sets.
  /** @type {string[]} */
  let aMatch = aStr.match(/\d+|\D+/g) || [];
  /** @type {string[]} */
  let bMatch = bStr.match(/\d+|\D+/g) || [];
  /** @type {number} */
  let length = Math.min(aMatch.length, bMatch.length);
  if (length <= 0) return 0;
  // Find which set is different.
  while (aMatch[i].toLowerCase() === bMatch[i].toLowerCase()) {
    i += 1;
    if (i >= length) {
      // At this point, a and b must be the same up to a certain point.
      // The shorter one should be before the longer one.
      return (aStr.length - bStr.length) * sign;
    }
  }
  // Use math or compare string values.
  if (/^\d+$/.test(aMatch[i]) && /^\d+$/.test(bMatch[i])) {
    return (Number(aMatch[i]) - Number(bMatch[i])) * sign;
  }
  return (aMatch[i].toLowerCase() > bMatch[i].toLowerCase() ? 1 : -1) * sign;
}