Javascript get name from email address | React Js

<!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">
      function getNameFromEmail(email) {
        const atIndex = email.indexOf("@");
        if (atIndex !== -1) {
          const name = email.substring(0, atIndex);
          return name;
        }
        return "";
      }
      const App = () => {
        const emails = [
          "john@example.com",
          "emma@example.com",
          "david@example.com",
          "sarah@example.com",
          "michael@example.com",
          "lisa@example.com",
          "alex@example.com",
          "olivia@example.com",
          "william@example.com",
          "natalie@example.com",
        ];

const names = emails.map((email) => getNameFromEmail(email));

return (
          <div className="container">
            <h1>React Js Get Name from Email Address</h1>
            <ul>
              {emails.map((email, index) => (
                <li key={index}>
                  Email: {email} | Name: {names[index]}
                </li>
              ))}
            </ul>
          </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;
      }
      .container h1 {
        font-size: 24px;
        margin-bottom: 20px;
      }

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

.container li {
        margin-bottom: 10px;
      }
    </style>
  </body>
</html>