TypeError:无法获取mern

Question

我的课程是"React，NodeJS，Express & MongoDB -- MERN全栈指南“部分，”连接React.js前端和后端“。有人能告诉我为什么会出现这个错误吗？每当我更新或删除一个位置时，它显示错误: TypeError: Failed fetch，我能对此做些什么？

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const UserPlaces = () => {
const [loadedPlaces, setLoadedPlaces] = useState();
const { isLoading, error, sendRequest, clearError } = useHttpClient();

const userId = useParams().userId;

useEffect(() => {
    const fetchPlaces = async () => {
        try {
            const responseData = await sendRequest(
                `http://localhost:5000/api/places/user/${userId}`
            );
            setLoadedPlaces(responseData.places);
        } catch (err) { }
    };
    fetchPlaces();

}, [sendRequest, userId]);

const placeDeletedHandler = deletedPlaceId => {
    setLoadedPlaces(prevPlaces =>
        prevPlaces.filter(place => place.id !== deletedPlaceId)
    );
};

return (
    <React.Fragment>
        <ErrorModal error={error} onClear={clearError} />
        {isLoading && (
            <div className="center">
                <LoadingSpinner />
            </div>
        )}
        {!isLoading && loadedPlaces && <PlaceList items={loadedPlaces} onDeletePlace={placeDeletedHandler} />}
    </React.Fragment>
);
};

export default UserPlaces;

前端：https://github.com/sharjeelyunus/peek-mern后端：https://github.com/sharjeelyunus/peek-mern-api

Answer 1

找到了答案:这是内核错误。您只需添加cors即可。

var cors = require('cors');

app.use(cors(), (req, res, next) = {}