Simple TODO Redux App

counter.js

import React from "react";
import { createStore } from "redux";

// ACTIONS
const createIncrement = amount => ({
  type: "INCREMENT",
  amount
});

const createDecrement = amount => ({
  type: "DECREMENT",
  amount
});

// REDUCER
function counterReducer(state = { count: 0 }, action) {
  switch (action.type) {
    case "INCREMENT":
      return { ...state, count: state.count + action.amount };
    case "DECREMENT":
      return { ...state, count: state.count - action.amount };
    default:
      return state;
  }
}

// STORE
const store = createStore(counterReducer, { count: 0 });

window.store = store;
window.createDecrement = createDecrement;
window.createIncrement = createIncrement;

const Playground = () => null;
export default Playground;

todo.js

import { createStore } from "redux";

// CREATE ACTIONS
const addTask = task => ({ type: "ADD_TASK", task });
const completeTask = task => ({ type: "COMPLETE_TASK", task });

// CREATE A REDUCER
function todos(state = [], action) {
  switch (action.type) {
    case "ADD_TASK":
      return [...state, { task: action.task, completed: false }];
    case "COMPLETE_TASK":
      return state.map(
        todo =>
          todo.task === action.task
            ? { task: action.task, completed: true }
            : todo
      );
    default:
      return state;
  }
}

// CREATE A STORE
const store = createStore(todos, []);