Force download for blob created with FileWriter in JavaScript

The download tag in combination with the Blob object does the trick (at least in the latest chrome versions). See this fiddle:

var blob = new Blob(['blaaaaat'], {type: 'text/plain'});
$('a').attr("href", window.URL.createObjectURL(blob));
$('a').attr("download", "woeii.txt");

F̶i̶r̶e̶f̶o̶x̶ ̶d̶o̶e̶s̶n̶'̶t̶ ̶s̶u̶p̶p̶o̶r̶t̶ ̶t̶h̶e̶ ̶d̶o̶w̶n̶l̶o̶a̶d̶ ̶a̶t̶t̶r̶i̶b̶u̶t̶e̶ though (it does support the Blob object). Discussions about implementation of the download attribute in Firefox are available here:

Edit: The download attribute is now supported by the latest firefox versions as of 10/3/2013