1const INCREMENT = "INCREMENT"; // define a constant for increment action types
2const DECREMENT = "DECREMENT"; // define a constant for decrement action types
3
4// define the counter reducer which will increment or decrement the state based on the action it receives
5const counterReducer = (state = 0, action) => {
6  switch (action.type) {
7    case INCREMENT:
8      return state + 1;
9
10    case DECREMENT:
11      return state - 1;
12
13    default:
14      return state;
15  }
16};
17
18// define an action creator for incrementing
19const incAction = () => {
20  return {
21    type: INCREMENT
22  };
23};
24
25// define an action creator for decrementing
26const decAction = () => {
27  return {
28    type: DECREMENT
29  };
30};
31
32// define the Redux store here, passing in your reducers
33const store = Redux.createStore(counterReducer);
34

1import React from 'react';
2
3class Counter extends React.Component {
4  state = { count: 0 }
5
6  increment = () => {
7    this.setState({
8      count: this.state.count + 1
9    });
10  }
11
12  decrement = () => {
13    this.setState({
14      count: this.state.count - 1
15    });
16  }
17
18  render() {
19    return (
20      <div>
21        <h2>Counter</h2>
22        <div>
23          <button onClick={this.decrement}>-</button>
24          <span>{this.state.count}</span>
25          <button onClick={this.increment}>+</button>
26        </div>
27      </div>
28    )
29  }
30}
31
32export default Counter;
33