React Js Array Push Method

<!DOCTYPE html>
<html>

<body>
    <div id="app"></div>
    <script type="text/babel">
        const { useState } = React;

function App() {
            const [items, setItems] = useState([]);
            const addItem = () => {
                const newItem = {
                    id: Date.now(),
                    name: 'Example',
                    quantity: items.length + 1,
                };

setItems((prevItems) => [...prevItems, newItem]);
            };

return (
                <div className="container">
                    <h3>React Js Add JSON Object to array</h3>
                    <button onClick={addItem}>Add Item</button>
                    <ul>
                        {items.map((item) => (
                            <li key={item.id}>
                                {item.name} - Quantity: {item.quantity}
                            </li>
                        ))}
                    </ul>
                </div>
            );
        }

ReactDOM.render(<App />, document.getElementById("app"));
    </script>
    <style>
        * {
            box-sizing: border-box;
        }

.container {
            margin: 0 auto;
            width: 600px;
            text-align: center;
            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 {
            color: #333;
            font-size: 24px;
            margin-bottom: 10px;
        }

button {
            padding: 10px 20px;
            background-color: #4caf50;
            color: white;
            border: none;
            border-radius: 4px;
            font-size: 16px;
            cursor: pointer;
        }

button:hover {
            background-color: #45a049;
        }

ul {
            list-style-type: none;
            padding: 0;
        }

li {
            padding: 8px 0;
            border-bottom: 1px solid #ddd;
        }

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

</html>

 
<!DOCTYPE html>
<html>
​
<head>
    <meta charset="UTF-8" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.2/umd/react.development.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.2/umd/react-dom.development.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.26.0/babel.min.js"></script>
</head>
​
<body>
    <div id="app"></div>
    <script type="text/babel">
        const { useState } = React;
​
        function App() {
            const [items, setItems] = useState([]);
            const addItem = () => {
                const newItem = {
                    id: Date.now(),
                    name: 'Example',
                    quantity: items.length + 1,
                };
​
                setItems((prevItems) => [...prevItems, newItem]);
            };
​
            return (
                <div className="container">
                    <h3>React Js Add JSON Object to array</h3>
                    <button onClick={addItem}>Add Item</button>
                    <ul>
                        {items.map((item) => (
                            <li key={item.id}>
                                {item.name} - Quantity: {item.quantity}
                            </li>
                        ))}
                    </ul>
                </div>
            );
        }
​
        ReactDOM.render(<App />, document.getElementById("app"));
    </script>
    <style>
        * {
            box-sizing: border-box;
        }
​
        .container {
            margin: 0 auto;
            width: 600px;
            text-align: center;
            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 {
            color: #333;
            font-size: 24px;
            margin-bottom: 10px;
        }
​
        button {
            padding: 10px 20px;
            background-color: #4caf50;
            color: white;
            border: none;
            border-radius: 4px;
            font-size: 16px;
            cursor: pointer;
        }
​
        button:hover {
            background-color: #45a049;
        }
​
        ul {
            list-style-type: none;
            padding: 0;
        }
​
        li {
            padding: 8px 0;
            border-bottom: 1px solid #ddd;
        }
​
        li:last-child {
            border-bottom: none;
        }
    </style>
</body>
​
</html>