jQuery Ajax to download a file

Has anyone downloaded files with a jQuery ajax call - to a web service would be ideal...

We fooled with MS Ajax Downloader stuff months ago - didn't like it and can't recall why.

Also did jDownload testing months ago - but that seems to be defunct now.

Anyone doing anything like this?

I want to download PDF files using ajax.

I found this code - and don't understand it much - but it's calling my download.aspx page

Code:

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$.download = function(url, data, method, callback){
    var inputs = '';
    var iframeX;
    var downloadInterval;
    if(url && data){
        // remove old iframe if has
        if($("#iframeX")) $("#iframeX").remove();
        // creater new iframe
        iframeX= $('<iframe src="[removed]false;" name="iframeX" id="iframeX"></iframe>').appendTo('body').hide();
        if($.browser.msie){
            downloadInterval = setInterval(function(){
                // if loading then readyState is “loading” else readyState is “interactive”
                if(iframeX&& iframeX[0].readyState !=="loading"){
                    callback();
                    clearInterval(downloadInterval);
                }
            }, 23);
        } else {
            iframeX.load(function(){
                callback();
            });
        }
        //split params into form inputs
        $.each(data, function(p, val){
            inputs+='<input type="hidden" name="'+ p +'" value="'+ val +'" />';
        });
        //create form to send request
        $('<form action="'+ url +'" method="'+ (method||'post') + '" target="iframeX">'+inputs+'</form>').appendTo('body').submit().remove();
    };
};

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I tried calling it like this - but the filename isn't passing in.

Code:

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$.download('Download.aspx', 'filename=mitlicense.txt');

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Can someone help explain to me the iframe and the input type HIDDEN stuff it's doing?

Thanks!