Success function not executing in ajax while using ashx hanler

Question

I am uploading data and image using ashx handler , they are working fine.

But my success function in ajax is not getting executed

See here:

  $.ajax({
                type: "POST",
                url: "../Scripts/uploadify/UploadHandler.ashx",
                contentType: false,
                processData: false,
                data: imag,
                success: function(data){
                    console.log(data.bb);
                    alert('hii');
                }

            });

Ashx:

       public void ProcessRequest(HttpContext context)

        {
           HttpPostedFile PostedFile = context.Request.Files[0];
        if (!(PostedFile == null))
         {
           |
           | 
          }
            context.Response.ContentType = "application/json";
            string bb = PostedFile.FileName;
            context.Response.Write(bb); //im getting bb name correctly suppose 'koyla.jpg'
            context.Response.StatusCode = 200;
        }
        public bool IsReusable
        {
         get
           {
        return false;
            }
        }

Im not getting bb in success function , alert is not even executing..???

Update:

       var fileUpload = $("#image").get(0);
            var files = fileUpload.files;

            var imag = new FormData();
            for (var i = 0; i < files.length; i++) {
                imag.append(files[i].name, files[i]);
                imag.append('Data',JSON.stringify({ objEnt: args }));

            }