JavaScript Template for Writing to a File through a Blob

The Blob object is a built-in JavaScript feature that allows you to create file-like objects of immutable raw data. Using a Blob, you can easily generate text files directly in the browser. Here's how to use it:

• Create a Blob object containing the data you want to write to a text file.
• Use the URL.createObjectURL() method to create a downloadable link.
• Trigger the file download automatically when the user clicks a button.

The (relevant) code:

    <div>
      <textarea id="textData" rows="6" cols="50" placeholder="Enter text to save"></textarea><br/><br/>
      <textarea id="fileName" rows="1" cols="50" placeholder="FILENAME.txt"></textarea><br/><br/>
      <button onclick="saveTextFromIdToId('textData', 'fileName')">Download Text File using saveTextFromIdToId(txt,file)</button>
    </div>
    <script>
function saveText(text, fileName="saved.txt") {
  var blob = new Blob([text], { type: 'text/plain' });
  var link = document.createElement('a');
  link.href = URL.createObjectURL(blob);
  link.download = fileName;
  link.click();
}

function saveTextFromIdToId(textareaId, fileNameId) {
  var text     = document.getElementById(textareaId).value;
  var fileName = document.getElementById(fileNameId).value;
  saveText(text,fileName);
}

(You may of course change the identifiers, forego embedding your textarea and button in a div element, etc.)