react-examples/clockupdate-stateful.htm at master · arvindpdmn/react-examples · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>React Stateful Clock Update</title>
</head>

<body>
    <div id="root"></div>

    <script src="https://unpkg.com/react@15/dist/react.js"></script>
    <script src="https://unpkg.com/react-dom@15/dist/react-dom.js"></script>
    <script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>

    <script type="text/jsx">
class Clock extends React.Component {
  constructor(props) {
    super(props);
    this.state = {date: new Date()};
  }

  tick() {
    this.setState({
      date: new Date()
    });
  }

  // When the Clock output is inserted in the DOM, React calls the componentDidMount() lifecycle hook.
  // Inside it, the Clock component asks the browser to set up a timer to call tick() once a second.
  componentDidMount() {
    this.timerID = setInterval(
      () => this.tick(),
      1000
    );
  }

  // If the Clock component is ever removed from the DOM,
  // React calls the componentWillUnmount() lifecycle hook so the timer is stopped.
  componentWillUnmount() {
    clearInterval(this.timerID);
  }

  render() {
    return (
      <div>
        <h1>Hello, world!</h1>
        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
      </div>
    );
  }
}

ReactDOM.render(
  <Clock />,
  document.getElementById('root')
);
    </script>
</body>

</html>