Is it possible to write data to file using only JavaScript?

Question

I want to Write Data to existing file using JavaScript. I don't want to print it on console. I want to Actually Write data to abc.txt. I read many answered question but every where they are printing on console. at some place they have given code but its not working. So please can any one help me How to actually write data to File.

I referred the code but its not working: its giving error:

Uncaught TypeError: Illegal constructor

on chrome and

SecurityError: The operation is insecure.

on Mozilla

var f = "sometextfile.txt";

writeTextFile(f, "Spoon")
writeTextFile(f, "Cheese monkey")
writeTextFile(f, "Onion")

function writeTextFile(afilename, output)
{
  var txtFile =new File(afilename);
  txtFile.writeln(output);
  txtFile.close();
}

So can we actually write data to file using only Javascript or NOT?

Answer 1

You can create files in browser using Blob and URL.createObjectURL. All recent browsers support this.

You can not directly save the file you create, since that would cause massive security problems, but you can provide it as a download link for the user. You can suggest a file name via the download attribute of the link, in browsers that support the download attribute. As with any other download, the user downloading the file will have the final say on the file name though.

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);

    // returns a URL you can use as a href
    return textFile;
  };

Here's an example that uses this technique to save arbitrary text from a textarea.

If you want to immediately initiate the download instead of requiring the user to click on a link, you can use mouse events to simulate a mouse click on the link as Lifecube's answer did. I've created an updated example that uses this technique.

  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);

    // wait for the link to be added to the document
    window.requestAnimationFrame(function () {
      var event = new MouseEvent('click');
      link.dispatchEvent(event);
      document.body.removeChild(link);
    });

  }, false);