redux-counter.js

import React from 'react';
import { createStore } from 'redux';
import { Provider, connect } from 'react-redux';

const View = props => (
  <div>
    <p>{props.count}</p>
    <button onClick={props.onClickIncrement}>+1</button>
    <button onClick={props.onClickDecrement}>-1</button>
  </div>
  );
const mapStateToProps = state => ({
  count: state.count,
});
const mapDispatchToProps = dispatch => ({
  onClickIncrement: () => {
    dispatch({
      type: 'increment',
    });
  },
  onClickDecrement: () => {
    dispatch({
      type: 'decrement',
    });
  },
});
const Container = connect(mapStateToProps, mapDispatchToProps)(View);

const reducer = (state, action) => {
  switch (action.type) {
    case 'increment':
      return { count: state.count + 1 };
    case 'decrement':
      return { count: state.count - 1 };
    default:
      return state;
  }
};
const initialState = { count: 0 };
const store = createStore(reducer, initialState);

export default () => (
  <Provider store={store}>
    <Container />
  </Provider>
);