ajax the file input

I am trying to submit multiple forms on same page at same time; with one of them being a file input.

The key is to wrap the form, using a new FormData.

  $.ajax({
    url: 'saveAttachment.do',
    type: 'POST',
    data: new FormData($('#saveAttachment')[0]),
    async: false,
    cache: false,
    contentType: false,
    processData: false,
    success: function (returndata) {
      alert(returndata);
    }
  });