stateful-component.html


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
        <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
    <script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
    <script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>

</head>
<body>
    <div id="timer-example"></div>

    <script type="text/babel">
      class Timer extends React.Component {
        constructor(props) {
          super(props);
          this.state = { seconds: 0 };
        }

        tick() {
          this.setState(state => ({
            seconds: state.seconds + 1
          }));
        }

        componentDidMount() {
          this.interval = setInterval(() => this.tick(), 1000);
        }

        componentWillUnmount() {
          clearInterval(this.interval);
        }

        render() {
          return (
            <div>
              Seconds: {this.state.seconds}
            </div>
          );
        }
      }

      ReactDOM.render(<Timer />, document.getElementById('timer-example'));
    </script>
</body>
</html>