redux-toolkit-example2.js

import { createAction, createReducer, configureStore } from '@reduxjs/toolkit'

const addTodo = createAction('ADD_TODO')
const toggleTodo = createAction('TOGGLE_TODO')

const todos = createReducer([], {
  [addTodo]: (state, action) => {
    const { id, text } = action.payload
    state.push({ id, text, completed: false })
  },
  [toggleTodo]: (state, action) => {
    const todo = state.find(todo => todo.id === action.payload)
    if (todo) {
      todo.completed = !todo.completed
    }
  }
})

const store = configureStore({ reducer: todos })