how to update component in react native code example

Example: lifecycles if reactjs

class Clock extends React.Component {
  constructor(props) {
    super(props);
    this.state = {date: new Date()};
  }

  componentDidMount() {  }
  componentWillUnmount() {  }
  render() {
    return (
      

        
Hello, world!
        
It is {this.state.date.toLocaleTimeString()}.
      
    );
  }
}