Minimal react-redux app - Shows what the 'connect' API does. Deployed at https://cranky-yonath-667b1f.netlify.com/

Counter.js

import React, { Component } from 'react'
import { render } from 'react-dom'
import { createStore } from 'redux'
import { connect, Provider } from 'react-redux'


// Reducer and Store
function counterReducer(state={value: 0}, action) {
  switch(action.type) {
    case 'INC':
      return Object.assign({}, state, {value: state.value + 1})
    default:
      return state
  }
}
const store = createStore(counterReducer)


// Pure Functional Component
const CounterFunc = ({value, onClick}) => {
  return (
    <div onClick={onClick} className='minimal-counter'>
      {value}
    </div>
  )
}


// react-redux functions
const mapStateToProps = state => state

const mapDispatchToProps = dispatch => {
  return {
    onClick: function() {
      return dispatch({type: 'INC'})
    }
  }
}

const ConnectedCounter = connect(
  mapStateToProps,
  mapDispatchToProps
)(CounterFunc)


// react-dom render
render(
  <Provider store={store}>
    <ConnectedCounter />
  </Provider>,
  document.getElementById('root')
)

index.css

body {
  margin: 0;
  padding: 5%;
  font-family: sans-serif;
  font-size: 1.5rem;
}

.minimal-counter {
  padding: 30px;
  font-size: 1.4em;
  border: 1px solid black;
  cursor: pointer;
  display: inline-block;
}