how to edit a fil with vanilla js

1(function () {
2    var textFile = null;
3  function makeTextFile(text) {
4    var data = new Blob([text], {type: 'text/plain'});
5
6    // If we are replacing a previously generated file we need to
7    // manually revoke the object URL to avoid memory leaks.
8    if (textFile !== null) {
9      window.URL.revokeObjectURL(textFile);
10    }
11
12    textFile = window.URL.createObjectURL(data);
13
14    return textFile;
15  }
16
17
18  var create = document.getElementById('create');
19  var textbox = document.getElementById('textbox');
20
21    //create a click event listener
22  create.addEventListener('click', function () {
23    var link = document.getElementById('downloadlink');
24    link.setAttribute('download', 'info.txt');
25    //make the text file
26    link.href = makeTextFile(textbox.value);
27    link.style.display = 'block';
28        //wait for the link to be rendered and then initiate a click to download the file
29     window.requestAnimationFrame(function () {
30      var event = new MouseEvent('click');
31      link.dispatchEvent(event);
32      document.body.removeChild(link);
33    });
34  }, false);
35
36})();