Simple JS function to validate NIT/PIS/PASEP numbers

ispis.js

function ispis(pis) {
  pis = pis.toString();
  var weight = [3, 2, 9, 8, 7, 6, 5, 4, 3, 2];
  var sum = 0, digito = 0;
  if (pis.length != 11 || pis.match(/\D/))
    return false;
  pis = pis.split("");
  for (var i=0; i < 10; i++)
    sum += weight[i] * pis[i];
  digito = 11 - (sum % 11);
  digito = digito < 10 ? digito : 0;
  return pis[10] == digito;
}