javascript - Download binary without triggering onbeforeunload

Question

I want to kick off a file download for a user when he clicks a link, but I have an onbeforeunload handler that I don't want to get invoked when the download begins. To downloads, I currently have an <a> with the href set to the file location but clicking it results in onbeforeunload being invoked in Chrome (not in FF, though).

I know I can set a private flag and check that in the onbeforeunload handler, but is there some way to kick off the download using ajax? I still want the user to see the usual dialogs when they download the file (Open/Save etc).

Ideas?

Answer 1

The best way to do this is indeed by constructing an iframe and triggering the download from there.

I have tested this in Chrome, IE6+ and Firefox and this approach seems to work in all of them.

Example code:

function DownloadFile(filePath) {
    var downloadIframe = $('<iframe />', 
        {
            id    :    'downloadIframe'        
        }).appendTo('body');
    downloadIframe.attr('src', filePath);
}

This will only work properly for a one off download (as we've hard coded an id), if you are triggering multiple downloads, then I suggest you reuse the iframe by storing it in a more widely accessible variable.