Failed to execute 'atob' on 'Window'

BlobBuilder is obsolete, use Blob constructor instead:

URL.createObjectURL(new Blob([/*whatever content*/] , {type:'text/plain'}));

This returns a blob URL which you can then use in an anchor's href. You can also modify an anchor's download attribute to manipulate the file name:

<a href="/*assign url here*/" id="link" download="whatever.txt">download me</a>

Fiddled. If I recall correctly, there are arbitrary restrictions on trusted non-user initiated downloads; thus we'll stick with a link clicking which is seen as sufficiently user-initiated :)

Update: it's actually pretty trivial to save current document's html! Whenever our interactive link is clicked, we'll update its href with a relevant blob. After executing the click-bound event, that's the download URL that will be navigated to!

$('#link').on('click', function(e){
  this.href = URL.createObjectURL(
    new Blob([document.documentElement.outerHTML] , {type:'text/html'})
  );
});

Fiddled again.


Here I got the error: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.

Because you didn't pass a base64-encoded string. Look at your functions: both download and dataURItoBlob do expect a data URI for some reason; you however are passing a plain html markup string to download in your example.

Not only is HTML invalid as base64, you are calling .split(',')[1] on it which will yield undefined - and "undefined" is not a valid base64-encoded string either.

I don't know, but I read that I need to encode my string to base64

That doesn't make much sense to me. You want to encode it somehow, only to decode it then?

What should I call and how?

Change the interface of your download function back to where it received the filename and text arguments.

Notice that the BlobBuilder does not only support appending whole strings (so you don't need to create those ArrayBuffer things), but also is deprecated in favor of the Blob constructor.

Can I put a name on my saved file?

Yes. Don't use the Blob constructor, but the File constructor.

function download(filename, text) {
    try {
        var file = new File([text], filename, {type:"text/plain"});
    } catch(e) {
        // when File constructor is not supported
        file = new Blob([text], {type:"text/plain"});
    }
    var url  = window.URL.createObjectURL(file);
    …
}

download('test.html', "<html>" + document.documentElement.innerHTML + "</html>");

See JavaScript blob filename without link on what to do with that object url, just setting the current location to it doesn't work.