How to make a browser display a "save as dialog" so the user can save the content of a string to a file on his system?

How can I make a browser display a "save as dialog" so the user can save the content of a string to a file on his system?

For example:

var myString = "my string with some stuff";
save_to_filesystem(myString,"myString.txt");

Resulting in something like this:

In case anyone is still wondering...

I did it like this:

<a href="data:application/xml;charset=utf-8,your code here" download="filename.html">Save</a>

can't remember my source but it uses the following techniques\features:

1. html5 download attribute
2. data URI's

Found the reference:

http://paxcel.net/blog/savedownload-file-using-html5-javascript-the-download-attribute-2/

EDIT: As you can gather from the comments, this does NOT work in

1. Internet Explorer (however works in Edge v13 and later)
2. Opera Mini

http://caniuse.com/#feat=download

There is a javascript library for this, see FileSaver.js on Github

However the saveAs() function won't send pure string to the browser, you need to convert it to blob:

function data2blob(data, isBase64) {
  var chars = "";

  if (isBase64)
    chars = atob(data);
  else
    chars = data;

  var bytes = new Array(chars.length);
  for (var i = 0; i < chars.length; i++) {
    bytes[i] = chars.charCodeAt(i);
  }

  var blob = new Blob([new Uint8Array(bytes)]);
  return blob;
}

and then call saveAs on the blob, as like:

var myString = "my string with some stuff";
saveAs( data2blob(myString), "myString.txt" );

Of course remember to include the above-mentioned javascript library on your webpage using <script src=FileSaver.js>

There is a new spec called the Native File System API that allows you to do this properly like this:

const result = await window.chooseFileSystemEntries({ type: "save-file" });

There is a demo here, but I believe it is using an origin trial so it may not work in your own website unless you sign up or enable a config flag, and it obviously only works in Chrome. If you're making an Electron app this might be an option though.

This is possible using this cross browser javascript implementation of the HTML5 saveAs function: https://github.com/koffsyrup/FileSaver.js

If all you want to do is save text then the above script works in all browsers(including all versions of IE), using nothing but JS.