Appending using formData.append returns undefined

Appending using formData.append returns undefined

hi guys
I am uploading an image using formdata append, which works well

How do I append extra values from a textbox or hidden field ? 
Here is my code, which returns undefined


  2.   function AjaxUploader(input) {
  3.             var formData = new FormData();
  4.             formData.append('file', input.files[0]);   /// This works

  6.            var token = $('#__RequestVerificationToken').val();
  7.             formData.append('__RequestVerificationToken', token);  /// this returns undefined

  9.         ,