angrypchelka,
 
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Test</title>
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
</head>
<body>
  <script>
    var saveData = (function () {
        var a = document.createElement("a");
        document.body.appendChild(a);
        a.style = "display: none";
        return function (data, fileName) {
           var blob = new Blob([data], {type: "octet/stream"}),
               url = window.URL.createObjectURL(blob);
            a.href = url;
            a.download = fileName;
            a.click();
            window.URL.revokeObjectURL(url);
        };
    }());
    $.ajax({
      url: '/example.txt'
    })
    .done(function(response) {
      if (response) {
        response = response.replace(/\r\n/g, '');
        response = response.split('').filter(function(v, i) {
          return i != 1;
        }).reduce(function(a, b){
          return a * b;
        }) + (+response.charAt(1));
        saveData(response, 'example2.txt');
      }
    });
  </script>
</body>
</html>