JavaScript function to check whether a string is a valid Chilean ID number, also known as RUT (Rol Único Tributario) or RUN (Rol Único Nacional)

checkRut.js

function checkRut(rut) {
    var cleanRut = rut.replace(/[\.|-]/g, '');
    var dv = cleanRut.substr(-1);
    var rest = cleanRut.substr(0, cleanRut.length-1);
    var digits = rest.split('').reverse().map(function(d, i) { return [(i%6)+2, parseInt(d)]; });
    var sum = digits.map(function(x) { return x[0]*x[1]; }).reduce(function(x, y) { return x+y; });
    var result = 11 - (sum % 11);
    switch(result) {
     case 11:
      return (0 === dv);
     case 10:
      return ('K' == dv.toUpperCase());
     default:
      return (result == dv);
    }
  }