I have a Jquery element of input type='file'.  
$('#test').prop('files')[0];
I'd like to change the #test to a string.
var all_data    = new FormData();
$('input[type="file"]').each(function(index) { 
    var i           = index+1;
    var input_name  = '#test'+i;
    var file_data   = $(input_name).prop('files')[0]; //I think error start here
    alert(file_data);
    all_data.append('file', file_data);
});
alert(all_data);
But, it's not working.
HTML in PHP script:
$jml = 3;
for($i=1;$i<=$jml;$i++){ 
   echo "<input type='file' name='test".$i."' id='test".$i."' 
}
 
     
    