const initialState = {

  count: 0

};

const reducer = (state = initialState, action) => {

  switch (action.type) {

    case 'INCREMENT':

      return { 

        ...state, 

        count: state.count + 1 

      }

    case 'DECREMENT':

      return { 

        ...state, 

        count: state.count - 1 

       }

    case 'RESET':

      return { 

        ...state, 

        count: state.count = 0

    }

    default:

      return state

  }

}

​

const store = Redux.createStore(reducer);

​

​

​

const Counter = (props) => {

  const { value, onIncrement, onDecrement, onReset } = props;

  return (

    <div>

        <h1>{value}</h1>

        <button onClick={onIncrement}>+</button>

        <button onClick={onReset}>Reset</button>

        <button onClick={onDecrement}>-</button>

    </div>

  );

}

​

const render = () => {

  ReactDOM.render(

    <Counter 

      value={store.getState().count}

      onIncrement={() => store.dispatch({ type : 'INCREMENT' })}

      onDecrement={() => store.dispatch({ type : 'DECREMENT' })}

      onReset={() => store.dispatch({ type : 'RESET' })}

    />,

    document.getElementById('root')

  );

};

​

store.subscribe(() => {

  console.log(store.getState());

  render();

})

render()

​

​

​

​

​

​

​

​

​

​