React Js Convert String into Sentance case

<!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 convertToSentenceCase(str) {
        if (!str) {
          return "";
        }

const lowerCaseStr = str.toLowerCase();
        const sentenceCaseStr =
          lowerCaseStr.charAt(0).toUpperCase() + lowerCaseStr.slice(1);

return sentenceCaseStr;
      }
      const App = () => {
        const inputString = "hello, world!";
        const convertedString = convertToSentenceCase(inputString);

return (
          <div className="container">
            <h3>React js Convert String into Sentance case </h3>
            <p>Original string: {inputString}</p>
            <p>Converted string: {convertedString}</p>
          </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>