<div class="root"></div>
     <script crossorigin src="https://unpkg.com/react@18/umd/react.development.js"></script>
     <script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script>
     <!-- <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script> -->
     <!-- <script type="module" src="/app.js"></script> -->
     <script>
        const test = React.createElement("h1", {}, "Hello this is react world!")
        const root = ReactDOM.createRoot(document.getElementsByClassName("root"))
        root.render(test)
     </script>

I tried to add above code in my react.js project. But it’s only working for id=”root” but not for class=”root”. Can anyone tell me why?