bodega.js

// remember that we have a store that we can call on to check the state
const store = Redux.createStore(toDoReducer, initialToDoState);  

// check the state
store.getState()

// initial state
{ toDos: [] }

// action ADD_TODO is dispatched with the value 'Buy Food'
const ADDTODO = ('Buy Food') => {
  type: 'ADD_TODO',
  toDo: 'Buy Food',
};
  
const toDoReducer = (state = initialToDoState, action) => {
  switch(action.type) {
    case 'ADD_TODO':
      // spread the current state and toDos array to save prior changes
      // add the new toDo to the toDos array
      return {
        ...state,
        toDos: [
          // spread the array as it's nested
          ...state.toDos,
          'Buy Food',
        ],
      };
      
    // default catch in case an action doesn't exist
    // this will return the initialState
    default:
      return state;
  };
};

// check state after action is dispatched and completed
store.getState()
{ toDos: [ 'Buy Food' ] }