lifecycles if reactjs

1class Clock extends React.Component {
2  constructor(props) {
3    super(props);
4    this.state = {date: new Date()};
5  }
6
7  componentDidMount() {  }
8  componentWillUnmount() {  }
9  render() {
10    return (
11      <div>
12        <h1>Hello, world!</h1>
13        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
14      </div>
15    );
16  }
17}

1componentDidMount()