Validación de CUIL (Argentina) en TypeScript / JavaScript

cuil-validator.ts

export function cuilValidator(cuil: string): boolean {
  if (cuil.length !== 11) {
    return false;
  }

  const [checkDigit, ...rest] = cuil
    .split('')
    .map(Number)
    .reverse();

  const total = rest.reduce(
    (acc, cur, index) => acc + cur * (2 + (index % 6)),
    0,
  );

  const mod11 = 11 - (total % 11);

  if (mod11 === 11) {
    return checkDigit === 0;
  }

  if (mod11 === 10) {
    return false;
  }

  return checkDigit === mod11;
}

is this correct?

This function seems to be more correct:

function validateCUITorCUIL(cuitOrCuil) {
  if (!/^\d{2}-\d{8}-\d$/.test(cuitOrCuil)) {
    return false;
  }

  var cuitOrCuilNoDash = cuitOrCuil.replace(/-/g, '');
  var checkDigit = parseInt(cuitOrCuilNoDash.charAt(10));
  var checkSum = 0;
  var multiplier = [5, 4, 3, 2, 7, 6, 5, 4, 3, 2];

  for (var i = 0; i < 10; i++) {
    checkSum += parseInt(cuitOrCuilNoDash.charAt(i)) * multiplier[i];
  }

  var result = (11 - checkSum % 11) % 11;
  return result === checkDigit;
}

@teebu elaborate "more correct"

I was looking for a validator, and stumbled on to this library https://github.com/brielov/cuit/tree/master/src and checked their tests.