reactintro/16.effect.cleanup.html at master · linyutg/reactintro · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <title>effect cleanup</title>
    <meta charset="utf-8" />
    <style>
      body {
        font-family: -apple-system, sans-serif;
      }
    </style>
  </head>
  <body>
    <div id="app"></div>
    <script src="react/react.js"></script>
    <script src="react/react-dom.js"></script>
    <script src="react/babel.js"></script>
    <script type="text/babel">
      const { useState, useEffect } = React;

      function RepeatMessage({ message }) {
        useEffect(() => {
          setInterval(() => {
            console.log(message);
          }, 2000);

          // return () => {
          //   clearInterval(id);
          // };
        }, [message]);

        return <div className="message">I'm logging to console "{message}"</div>;
      }

      export default function App() {
        const [message, setMessage] = useState("Hello, World!");

        return (
          <div className="App">
            <h3>Type the message to log to console</h3>
            <input type="text" value={message} onChange={(e) => setMessage(e.target.value)} />
            <RepeatMessage message={message} />
          </div>
        );
      }

      ReactDOM.render(<App />, document.getElementById("app"));
    </script>
  </body>
</html>