How Can JavaScript Write Data to a File for Download?

Writing Data to File in JavaScript

While JavaScript does not natively support file writing, it can still be achieved through the clever use of Blobs and URL.createObjectURL.

Browsers allow the creation of files using these methods. However, due to security concerns, direct saving of created files is prohibited. Instead, a download link can be provided to the user. Browsers may support the "download" attribute, which allows you to suggest a file name.

The code below provides a function to generate a text file from given text:

var makeTextFile = function (text) {
  var data = new Blob([text], {type: 'text/plain'});
  return window.URL.createObjectURL(data);
};

To initiate a download from a textarea, you can use the following code:

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

create.addEventListener('click', function () {
  var link = document.createElement('a');
  link.setAttribute('download', 'info.txt');
  link.href = makeTextFile(textbox.value);
  document.body.appendChild(link);

  // simulate mouse click on link to start download
  var event = new MouseEvent('click');
  link.dispatchEvent(event);
  document.body.removeChild(link);
});

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