React Js Convert object or array to String

<!DOCTYPE html>
<html>

<body>
    <div id="app"></div>
    <script type="text/babel" data-presets="env,react">
        const { useState } = React;

function App() {
            const [testObj, setTestObj] = useState({
                firstName: "David",
                lastName: "Warner",
                role: "Opener",
            });

return (
                <div className='container'>
                    <h2>React Js Convert JSON to string | JSON.stringify()</h2>
                    <p>String: {JSON.stringify(testObj)}</p>
                </div>
            );
        }

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

</body>

</html>

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<!DOCTYPE html>
<html>
​
<head>
    <meta charset="UTF-8" />
    <script src="https://unpkg.com/react@17.0.2/umd/react.development.js"></script>
    <script src="https://unpkg.com/react-dom@17.0.2/umd/react-dom.development.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/@babel/standalone@7.14.6/babel.min.js"></script>
</head>
​
<body>
    <div id="app"></div>
    <script type="text/babel" data-presets="env,react">
        const { useState } = React;
​
        function App() {
            const [testObj, setTestObj] = useState({
                firstName: "David",
                lastName: "Warner",
                role: "Opener",
            });
​
            return (
                <div className='container'>
                    <h2>React Js Convert JSON to string | JSON.stringify()</h2>
                    <p>String: {JSON.stringify(testObj)}</p>
                </div>
            );
        }
​
        ReactDOM.render(<App />, document.getElementById("app"));
    </script>
​
</body>
​
</html>