Javascript 获取错误通知失败

我想显示一个错误通知时，它有它的内部错误，但这是不工作，我希望你能帮助我谢谢

   export const deleter = (url, params) => {
        return(dispatch, getState, api) => {
                api += 'api/';
            return fetch(`${api}${url}`, {
                method: 'DELETE',
                headers: {
                    'Content-Type': 'application/json'
                },
                body: JSON.stringify(params)
            })
            .then(response => response.json())
            .then(result => dispatch(departmentResult(result, types.DELETER)))
            .catch(err => {
                    const errStatus = err.response ? err.response.status : 500;
                    if (errStatus == 500 || errStatus == 404){
                      return (NotificationManager.error('Sorry but this has already been used', 'ERROR! '));
                    } else {
                       return (NotificationManager.error('Sorry but this has already been used', 'ERROR! '));
                    }
           });
        }
    }