Javascript String isCPF()

String.prototype.isCPF = function(){
 var c = this;//from ww  w  . ja va2 s  .c o m
 if((c = c.replace(/[^\d]/g,"").split("")).length != 11) return false;
 if(new RegExp("^" + c[0] + "{11}$").test(c.join(""))) return false;
 for(var s = 10, n = 0, i = 0; s >= 2; n += c[i++] * s--);
  if(c[9] != (((n %= 11) < 2) ? 0 : 11 - n)) return false;
 for(var s = 11, n = 0, i = 0; s >= 2; n += c[i++] * s--);
  if(c[10] != (((n %= 11) < 2) ? 0 : 11 - n)) return false;
 return true;
}