Learn the basic of Redux in one file.

understanding_redux.js

const {createStore} = Redux;

const initState = {
  todos: [],
  posts: []
}

function myReducer(state=initState, action) {
  if (action.type === 'ADD_TODO') {
    return {
      ...state,
      todos: [...state.todos, action.payload]
    }
  } 
  
  if (action.type === 'ADD_POST') {
    return {
      ...state, 
      posts: [...state.posts, action.payload]
    }
  }
}

const store = createStore(myReducer);

store.subscribe(() => {
  console.log("STATE UPDATED");
  console.log(store.getState());
})

const todoAction = { type: 'ADD_TODO', payload: 'Buy Milk' }

store.dispatch({type: 'ADD_TODO', payload: "Sleep More"})
store.dispatch({type: 'ADD_TODO', payload: "Go to Store"})

store.dispatch({type: 'ADD_POST', payload: "This is a post, not a todo"})
store.dispatch({type: 'ADD_POST', payload: "This is a second post, not the first one"})