Handle duplicate value error in CRUD app (react-redux + express-mongoose)
As mentioned in comments, I think you have .then() on your json() instead of on your fetch(). You need something of the shape:
export const addNewCar = car => { console.log(car); return dispatch => { dispatch(addNewCarRequest(car)); return fetch(apiUrl, { method: "post", body: car }) .then(response => { if (response.ok) { return response.json(); } else { throw Error('blah') } }) .then(data => { console.log(data.car); dispatch(addNewCarRequestSuccess(data.car, data.message)); }) .catch(error => { dispatch(addNewCarRequestFailed(error)); }); };};