AM - get data about auctions

gistfile1.js

var lcs = function(a, b) {
  var aSub = a.substr(0, a.length-1);
  var bSub = b.substr(0, b.length-1);
 
  if (a.length == 0 || b.length == 0) {
    return "";
  } else if (a.charAt(a.length-1) == b.charAt(b.length-1)) {
    return lcs(aSub, bSub) + a.charAt(a.length-1);
  } else {
    var x = lcs(a, bSub);
    var y = lcs(aSub, b);
    return (x.length > y.length) ? x : y;
  }
};

var unique = function(arr){
  return arr.reverse().filter(function(el, i){
    return arr.indexOf(el, i+1) === -1;
  }).reverse();
};

var get = function(url, fn){
  var xhr = new XMLHttpRequest();
  xhr.open('GET', url);
  xhr.onabort = xhr.onerror = function(){
    fn(false);
  };
  xhr.onreadystatechange = function(resp){
    if( xhr.readyState === 4 ){
      fn(resp.target.responseText, resp);
    }
  };
  xhr.send();
};

if( typeof links === 'undefined' ){
  var links = unique(prompt().trim().split(/\n/));
}
var res = [];

(function check(i, sum){
  if( typeof links[i] === 'undefined' ){
    console.log('Ilość wystwaionych domen: ' + sum);
    return alert('done');
  }
  get(links[i], function(html){
    var num = parseInt(html.match(/lista domen \(([0-9]+)\)/)[1], 10);
    var tf = html.match(/\<textarea[^\>]*\>([\s\S]+)\<\/textarea\>/im)[1];
    var spl = (tf).trim().split(/\n/);
    var lcsRes = spl[0];
    spl.map(function(line){
      lcsRes = lcs(lcsRes, line);
    });
    console.log([links[i], ' (', num, ') ', lcsRes, "\n"].join(''));
    check(i+1, sum + num);
  });
})(0, 0);