从ajax响应中下载二进制文件

Question

I have an Excel file which I upload using JavaScript. Once it is uploaded I perform some operations on it. Then I create a new Excel file from that data which is further downloaded.

Now everything is working fine, but the ajax response is returning a binary result of the output file. I want to download this file. The result of console.log is:

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$('#subb').on('click', function() {
    var file_data = $('#excel_upload').prop('files')[0];   
    var form_data = new FormData();                  
    form_data.append('file', file_data);
    $.ajax({
        url: 'processing.php', // point to server-side PHP script 
        dataType: 'text',  // what to expect back from the PHP script, if anything
        cache: false,
        contentType: false,
        processData: false,
        data: form_data,                         
        type: 'post',
        success: function(data){
          var a = document.createElement('a');
            var url = data;
            a.href = url;
            a.download = 'myfile.pdf';
            a.click();
            window.URL.revokeObjectURL(url);
        }
     });
});

So any idea how to convert the binary file into excel and further download it

EDIT 1: So i solved it. Below is the javascript code i wrote

$('#submit_btn').on('click', function() {
    var file_data = $('#excel_upload').prop('files')[0];   
    var form_data = new FormData();                  
    form_data.append('file', file_data);
    $.ajax({
        url: 'process.php', // point to server-side PHP script 
        dataType: 'json',  // what to expect back from the PHP script, if anything
        cache: false,
        contentType: false,
        processData: false,
        data: form_data,                         
        type: 'post',
        beforeSend: function() {
        $("#submit_btn").html('<img src="https://thumbs.gfycat.com/UnitedSmartBinturong-max-1mb.gif" style="height:20px">');
        },
        success: function(data){
            var a = $("<a>");
            a.attr("href",data.file);
            $("body").append(a);
            a.attr("download","file.xls");
            a[0].click();
            a.remove(); 
            $("#submit_btn").html('Submit');
        }
        });

}); 

And at the server end

$writer->save('php://output');
$xlsData = ob_get_contents();
ob_end_clean();
$response=array('file'=>"data:application/vnd.msexcel;base64,"base64_encode($xlsData));
die(json_encode($response));

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