create_txt.html

<input class="checkit" type="checkbox" name="daftar" value="Bike"> I have a bike<br>
<input class="checkit" type="checkbox" name="daftar" value="Car" checked> I have a car<br>
<input class="checkit" type="checkbox" name="daftar" value="Pen" checked> I have a Pen<br>

<input type="button" onclick="alert(getCheckedCheckboxesFor('daftar'));" value="Get Values" />
<button id="create">Create file</button> 
<a download="info.txt" id="downloadlink" style="display: none">Download</a>
<script>

function getCheckedCheckboxesFor(checkboxName) {
  var checkboxes = document.querySelectorAll('input[name="' + checkboxName + '"]:checked'), values = [];
  // Array.prototype.forEach.call(checkboxes, function(el) {
  //     values.push(el.value);
  // });

  values = "";
  for(var i=0;i< checkboxes.length; i++){
    values += checkboxes[i].value + "\n";
  }

  return values;
}

function myValues(selector) {
  var checkboxArray = document.querySelectorAll(selector);

  var myOutputText = "";
  for(var i=0;i< checkboxArray.length; i++){
    if (checkboxArray[i].checked) {
      myOutputText += checkboxArray[i].value + "\n";
    }
  }

  return myOutputText;
}

var textFile = null;
var makeTextFile = function (text) {
  var data = new Blob([text], {type: 'text/plain'});

  // If we are replacing a previously generated file we need to
  // manually revoke the object URL to avoid memory leaks.
  if (textFile !== null) {
    window.URL.revokeObjectURL(textFile);
  }

  textFile = window.URL.createObjectURL(data);

  return textFile;
};


var create = document.getElementById('create');  

create.addEventListener('click', function () {
  var link = document.getElementById('downloadlink');
  link.href = makeTextFile(myValues('.checkit'));
  link.style.display = 'block';
}, false);

</script>