Redux store does not have a valid reducer - reactjs

Question

Haven't been able to find anything around here regarding this error:
"Store does not have a valid reducer. Make sure the argument passed to combineReducers is an object whose values are reducers."
My reducer
export default function FriendListReducer(state = {friends : []}, action) {
switch (action.type) {
case 'ADD_FRIEND':
return [
{ friends : action.payload.friend }, ...state.friends
]
default:
return state;
}
return state;
}
Combiner
import { combineReducers } from 'redux';
import { FriendListReducer } from './FriendListReducer';
const rootReducer = combineReducers({
friends: FriendListReducer
});
export default rootReducer;
My store config
import { applyMiddleware, createStore } from 'redux';
import thunkMiddleware from 'redux-thunk';
import createLogger from 'redux-logger';
import rootReducer from '../reducers/reducers';
export default function configureStore(initialState = { friends: [] }) {
const logger = createLogger({
collapsed: true,
predicate: () =>
process.env.NODE_ENV === `development`, // eslint-disable-line no-unused-vars
});
const middleware = applyMiddleware(thunkMiddleware, logger);
const store = middleware(createStore)(rootReducer, initialState);
if (module.hot) {
// Enable Webpack hot module replacement for reducers
module.hot.accept('../reducers/reducers', () => {
const nextRootReducer = require('../reducers/reducers').default;
store.replaceReducer(nextRootReducer);
});
}
return store;
}

Answer 1

Your import statement is incorrect. Either you use import { Foo } from 'bar' together with export Foo, or use import Foo from 'bar' if you export with export default Foo.
In other words, change either export default function FriendListReducer to export function FriendListReducer, or change the import statement from import { FriendListReducer } to import FriendListReducer.

Answer 2

If the object is empty.
export default combineReducers({
})
This error will show.

Answer 3

../reducers/reducers ? it's a strange naming
Anyway, it seems ../reducers/reducers doesn't return a reducer, if reducers is a directory, put a index.js inside, import each reducer and create a root reducer
import FriendListReducer from "./FriendListReducer"
const rootReducer = combineReducers({
friendList : FriendListReducer
})
export default rootReducer
Important!! you will have state.friendList in your state.
I hope it will help

Answer 4

store.js
FALSE
import { charactersSlice } from "./charactersSlice.js";
TRUE NOT USING {}
import charactersSlice from "./charactersSlice.js";

Answer 5

It looks like your top-level reducer function is using an array as its default value. Redux expects that the very top of your state will be an object, not an array. Try putting the array at a particular key in that object, like { friendList : [] }.

Answer 6

on above your codes
import { FriendListReducer } from './FriendListReducer';
const rootReducer = combineReducers({
friends: FriendListReducer
});
export default rootReducer;
instead of import { FriendListReducer } from './FriendListReducer';
just say import FriendListReducer from './FriendListReducer';
since FriendListReducer was exported with export default FriendListReducer and not export const FriendListReducer

Answer 7

Please check your combine reducer file It's empty......
you have forgot bind reducer here
import {combineReducers, createStore} from 'redux'
import listDataReducer from '../reducers/ListDataReducer'
const rootReducer = combineReducers({
listDataReducer, // Please add your reducer here
});
export default rootReducer;

Answer 8

I also faced the problem.
What I did was instead of:
combineReducers(productReducer, cartReducer)
I did:
combineReducers({ productReducer, cartReducer })
and it worked.
It expects a valid object for the store.