Chillean RUT validation

rut-validation.ts

/**
 * Provide string of type 12.333.333-k|123456789|12345678-9|12.345678-9
 * ???
 * profit.
 * @param {string} _rut
 * @returns {boolean}
 */
function isValidRUT(_rut) {
  const isRegexValid = _rut.match(/^\d{1,2}\.?\d{3}\.?\d{3}\-?[0-9kK]$/ig);
  if (!isRegexValid) return false;
  /** return early if the provided string is not worthy */

  const rut = _rut.replace(/\D/ig, '');
  /** replace everything that's not a digit from the pool */

  const rest = 11 - ([3, 2, 7, 6, 5, 4, 3, 2]
    .reduce((_total, multiplier, index) => _total  + (multiplier * +rut[index]), 0) % 11);
  /** subtract eleven to the sum of the magic multiplication and the module of elven */
  
  const lastChar = _rut[_rut.length - 1];

  if (rest < 11 && ('' + rest) === lastChar) return true;
  /** if the rest is less than elven and equal to the provided strings last character */
  
  return rest === 11 && lastChar === '0' || rest === 10 && lastChar.search(/[kK]/ig) > -1;
  /** Otherwise check if rest is eleven, or ten, and equal to 0 or K respectively */
};