I'm trying to make a post request to the server,but it returns 400 error. : this is react function

const handleSubmit = () => {
  const bookInstanceObject = {
    imprint: imprint,
  };

  axios
    .post('http://localhost:3001/catalog/bookinstance/create', bookInstanceObject)
    .then(res => {
      console.log(res.data);
    })
    .catch(error => {
      console.log(error);
    });
};

and this is the server side:

router.post('/bookinstance/create', (request, response, next) => {
  const body = request.body;

  const bookInstance = new BookInstance({
    imprint: body.title,
  });

  bookInstance
    .save()
    .then(savedBook => {
      response.json(savedBook.toJSON());
    })
    .catch(error => next(error));
});

any idea ?