React Js Get first index of item in array

<!DOCTYPE html>
<html>

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

function App() {
            const [result, setResult] = useState("");
            const country = [
                "China",
                "India",
                "United States",
                "Indonesia",
                "Pakistan",
            ];
            const myFunction = () => {
                setResult(country.indexOf("India"));
            };

return (
                <div className='container'>
                    <h2>React Js Get first index of item in array</h2>
                    <button onClick={myFunction} className="btn btn-primary">
                        Find Index of India
                    </button>
                    {result !== "" && (
                        <p>First Index of item in array: {result}</p>
                    )}
                </div>
            );
        }

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

h2 {
            font-size: 24px;
            margin-bottom: 10px;
        }

.btn {
            padding: 10px 20px;
            font-size: 16px;
            background-color: #007bff;
            color: #fff;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }

.btn:hover {
            background-color: #0056b3;
        }

p {
            margin-top: 20px;
        }
    </style>
</body>

</html>

xxxxxxxxxx
 
<!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 [result, setResult] = useState("");
            const country = [
                "China",
                "India",
                "United States",
                "Indonesia",
                "Pakistan",
            ];
            const myFunction = () => {
                setResult(country.indexOf("India"));
            };
​
            return (
                <div className='container'>
                    <h2>React Js Get first index of item in array</h2>
                    <button onClick={myFunction} className="btn btn-primary">
                        Find Index of India
                    </button>
                    {result !== "" && (
                        <p>First Index of item in array: {result}</p>
                    )}
                </div>
            );
        }
​
        ReactDOM.render(<App />, document.getElementById("app"));
    </script>
​
    <style>
        .container {
            margin: 20px;
            padding: 20px;
            border: 1px solid #ccc;
            border-radius: 5px;
            text-align: center;
        }
​
        h2 {
            font-size: 24px;
            margin-bottom: 10px;
        }
​
        .btn {
            padding: 10px 20px;
            font-size: 16px;
            background-color: #007bff;
            color: #fff;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }
​
        .btn:hover {
            background-color: #0056b3;
        }
​
        p {
            margin-top: 20px;
        }
    </style>
</body>
​
</html>