React Js Array Unshift() Method

<!DOCTYPE html>
<html>

<body>
    <div id="app"></div>
    <script type="text/babel">
        const { useState, useEffect } = React;
        function App() {
            const [array, setArray] = useState([4, 5, 6]);

const insertElements = () => {
                const elementsToInsert = [1, 2, 3];
                const newArray = [...elementsToInsert, ...array];
                setArray(newArray);
            };

return (
                <div className='container'>
                    <h2>React Js Insert Multiple element to starting of Array</h2>
                    <button onClick={insertElements}>Insert Elements</button>
                    <ul>
                        {array.map((item, index) => (
                            <li key={index}>{item}</li>
                        ))}
                    </ul>
                </div>
            );
        }

ReactDOM.render(<App />, document.getElementById('app'));
    </script>
    <style>
        .container {
            width: 600px;
            margin: 0 auto;
            box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.12), 0 2px 4px 0 rgba(0, 0, 0, 0.24);
            padding: 20px;
        }

h3 {
            margin-top: 0;
            font-size: 24px;
            color: #333;
        }

button {
            padding: 10px 20px;
            font-size: 16px;
            color: #fff;
            background-color: #007bff;
            border: none;
            border-radius: 4px;
            cursor: pointer;
            transition: background-color 0.3s ease;
        }

button:hover {
            background-color: #0056b3;
        }

ul {
            margin-top: 20px;
            padding-left: 0;
        }

li {
            list-style-type: none;
            padding: 10px 0;
            font-size: 18px;
            color: #333;
            border-bottom: 1px solid #ddd;
        }

li:last-child {
            border-bottom: none;
        }
    </style>
</body>

</html>