1Html
2<div id="app"></div>
3
4Css
5button{
6  width: 80px;
7  height: 40px;
8  margin: 15px;
9}
10.blackButton{
11  background-color: black;
12  color: white;
13}
14
15.whiteButton{
16  background-color: white;
17  color: black;
18}
19
20React
21class Test extends React.Component {
22  constructor(){
23         super();
24
25         this.state = {
26              black: true
27         }
28    }
29
30    changeColor(){
31        this.setState({black: !this.state.black})
32    }
33
34    render(){
35        let btn_class = this.state.black ? "blackButton" : "whiteButton";
36
37        return (
38             <div>
39                 <button className={btn_class}
40                         onClick={this.changeColor.bind(this)}>
41                           Button
42                  </button>
43             </div>
44        )
45    }
46}
47
48ReactDOM.render(<Test />, document.querySelector("#app"))
49