Create a download link from a Blob URL

Question

In a Google chrome extension I am working on, a file is downloaded from a server with an XMLHttpRequest. This file contains some binary data which are stored in an ArrayBuffer object. In order to provide the possibility to download this file I am using the createObjectURL API.

function publish(data) {
  if (!window.BlobBuilder && window.WebKitBlobBuilder) {
    window.BlobBuilder = window.WebKitBlobBuilder;
  }
  var builder = new BlobBuilder();
  builder.append(data);
  var blob = builder.getBlob();
  var url = window.webkitURL.createObjectURL(blob);
  $("#output").append($("<a/>").attr({href: url}).append("Download"));

}

It is working fine; except that the filename is an opaque UUID like 9a8f6a0f-dd0c-4715-85dc-7379db9ce142. Is there any way to force this filename to something more user-friendly?

Answer 1

you can force an arbitrary filename by setting the "download" attribute of your anchor

see: http://updates.html5rocks.com/2011/08/Downloading-resources-in-HTML5-a-download

Answer 2

I have never tried it before, but it should be possible to create a new File object (which allows you to specify a file name) and write your blob to it. Something along the lines of:

function publish(data, filename) {

    if (!window.BlobBuilder && window.WebKitBlobBuilder) {
        window.BlobBuilder = window.WebKitBlobBuilder;
    }

    fs.root.getFile(filename, {
        create: true
    }, function (fileEntry) {

        // Create a FileWriter object for our FileEntry (log.txt).
        fileEntry.createWriter(function (fileWriter) {

            fileWriter.onwriteend = function (e) {
                console.log('Write completed.');
            };

            fileWriter.onerror = function (e) {
                console.log('Write failed: ' + e.toString());
            };

            var builder = new BlobBuilder();
            builder.append(data);
            var blob = builder.getBlob();
            fileWriter.write(blob);

        }, errorHandler);

    }, errorHandler);
}

I think this could work for you.