response ajax download pdf (laravel 5)

My html code is like this :

<a href="javascript:;" onclick="showAjaxPdf('{{ $row->file_path }}');"><i class="fa fa-file-pdf-o"></i></a>

My javascript code is like this :

function showAjaxPdf(file_path)
        {
            var file_path = file_path.replace(/\\/g,"/");
            //example : file_path = assets/images/myfile.pdf
            $.ajax({
                type: "POST",
                data: 'file_path=' + file_path,
                url: "news/test",
                success: function(response)
                {
                    $('#test').html(response);

                }
            });
        }

My function test in controller :

public function postTest(Request $request)
    {
$file_path = $request->input('file_path');  
        return response()->download($file_path);       
    }

When I click on the pdf icon, no response.

I wish, when click on the pdf icon, appear like this:

how to keep the current click pdf icon, the image appears like it?

Thank you

via Chebli Mohamed