Uncaught error: “reducer” is a required argument, and must be a function or an object of functions that can be passed to combinereducers

Uncaught Error: “reducer” is a required argument, and must be a function or an object of functions that can be passed to combineReducers.

In Redux, the combineReducers function is used to combine multiple reducers into a single rootReducer. It takes an object as an argument, where each key represents a slice of state and each value represents the reducer function associated with that slice.

The error message you encountered suggests that the “reducer” argument provided to combineReducers is either missing or not a function or object of functions. To resolve this error, make sure you pass the correct argument to combineReducers.

Examples:

Let’s say you have two reducers: userReducer and postReducer. To combine them into a single rootReducer:

        
import { combineReducers } from 'redux';

// User Reducer
const userReducer = (state = {}, action) => {
    // reducer logic
    return state;
}

// Post Reducer
const postReducer = (state = [], action) => {
    // reducer logic
    return state;
}

// Combine Reducers
const rootReducer = combineReducers({
    user: userReducer,
    posts: postReducer
});

// Sample Redux store
const store = createStore(rootReducer);
        
    

In this example, combineReducers takes an object with two key-value pairs. The keys ‘user’ and ‘posts’ represent the respective slices of state in the Redux store. The values userReducer and postReducer are the reducer functions associated with those state slices.

Make sure the reducer functions you pass to combineReducers are valid functions that handle state updates correctly. If you’re importing your reducers from other files, double-check that you imported them correctly.