Question

Is it possible, in Javascript, to prompt user for downloading a file that isn’t actually on the server, but has contents of a script variable, instead?

Something in spirit with:

var contents = "Foo bar";
invoke_download_dialog(contents, "text/plain");

Cheers,

MH

Answer 1

javascript: URIs should work for this – indeed, this is exactly what they’re meant for. However, IE doesn’t honour the type attribute, and in Safari this technique has no effect at all.

data: URIs work in Firefox (3.0.11) and Safari (4.0) (and probably other compliant browsers), but I can’t get this approach to work in IE (8.0). (All tested in Windows)

<a href="data:text/plain,The%20quick%20brown%20fox%20jumps%20over%20the%20lazy%20dog.">Data URI</a>

This isn’t a JS solution in itself, but JS can be used to set the href dynamically. Use the escape function to turn raw text/data into URI-encoded form.

Combining this with detecting IE and using the IE-specific solution already linked to might do what you want….

I shall add that you can’t force it to trigger a download dialog (that’s beyond the scope of both HTML and JS), but you can persuade it to do so by setting application/octet-stream as the type. Trouble is that the user’ll then have to add the right filename extension manually.