React Check if String is Empty

<!DOCTYPE html>
<html>

<body>
    <div id="app"></div>
    <script type="text/babel">
        const App = () => {
            const str = " ";
            let message;
            if (!str || str.trim() === "") {
                message = "String is empty";
            } else {
                message = "String has some Value ";
            }
            return (
                <div className='container'>
                    <h1>React Js Check String is empty</h1>
                    <h3>{message}</h3>
                </div>
            );
        };

ReactDOM.render(<App />, document.getElementById("app"));
    </script>
    <style>
        .container {
            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);
            width: 600px;
            margin: 0 auto;
            padding: 20px;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
        }
    </style>
</body>

</html>