Simple React Redux state returns undefined

Question

I am completely stumped on this one. I've built the simplest of simple react redux component that currently only shows a counter held in the store. However this counter is always returned as undefined!

I'd expect the counter to return 0 as this is what's set in the reducer!

I've followed countless tutorials and I'm getting no where!

//index.js

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import {Provider} from 'react-redux';
import {createStore} from 'redux';
import counterReducer from './reducers/counterReducer';

const store = createStore(counterReducer);

ReactDOM.render(
  <React.StrictMode>
    <Provider store={store}>
    <App />
    </Provider>
  </React.StrictMode>,
  document.getElementById('root')
);

and

//app.js

import React from 'react';
import { useSelector } from 'react-redux'; 


function App() {
  const counter = useSelector(state => state.counter)
  return (
    <div className="App">
      <p>{`counter is ${counter}`}</p>
    </div>
  );
}

export default App;

and

//actions.js

export const add = (nr) =>{
    return {
        type: 'ADD',
        payload:{
            nr
        }
    }
}

and

//counterReducer.js

const counterReducer = (state=0, action) => {
    switch(action.type){
        case "ADD":
            return state+1;
        default:
            return state;
    }
}

export default counterReducer;

So as you can see it's a real simple setup. I'd expect the counter to return 0 as this is the initial state set in counterReducer.js

However I just get "counter is undefined" on the frontend!

Answer 1

either remove .counter from state

// already a number
const counter = useSelector(state => state)

---

or add counter to your redux root object:

import {createStore, combineReducers } from 'redux';
import counterReducer from './reducers/counterReducer';

const store = createStore(combineReducers({counter: counterReducer});