JSFiddle - React, Tailwind, and code Playground

HTML

<tr> <td>appKey</td>
                <td><input type="text" id="_appKey" size="40"></td>
                    <a download="info.txt" class="downloadlink" >Download</a> </p>

            </tr>
            <tr>
                <td>bundleId</td>
                <td><input type="text" id="_bundleId" size="40"></td>
                     <a download="info.txt" class="downloadlink" >Download</a> </p>
            </tr>
            <tr>
                <td>serverURL</td>
                <td><input type="text" id="_serverURL" size="40"></td>
                     <a download="info.txt" class="downloadlink" >Download</a> </p>
            </tr>

JavaScript

(function () {
var textFile = null,
  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 inputFields = document.getElementsByTagName('input');

      for(var i = 0; i < inputFields.length; i++) {
          (function(i){
          inputFields[i].addEventListener('keyup', function () {
              console.log(inputFields[i].value)
              var link = document.getElementsByClassName('downloadlink')[i];
              link.href = makeTextFile(inputFields[i].value);
          });
          })(i);
      }
})();