I am creating redux app using createSlice(), but get the error:

Error: The slice reducer for key "pageName" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined. If you don't want to set a value for this reducer, you can use null instead of undefined.

Here is the minimal example for this error.

pageNameSlice.js:

import { createSlice } from "@reduxjs/toolkit";

const pageNameSlice = createSlice({
    name: 'pageName',
    initalState: "",
    // The `reducers` field lets us define reducers and generate associated actions
    reducers: {
      setPageName: (state, newName) => {
          state.pageName = newName
      }
    }
});

export default pageNameSlice.reducer;

store.js:

import { configureStore } from '@reduxjs/toolkit';
import pageNameReducer from '../features/pageNameSlice';

export const store = configureStore({
  reducer: {
    pageName: pageNameReducer
  },
});