My code is very simple. I checked all the resources, rewrote the code into different files, updated my computer, checked the css files and everything is fine and I can't see the problem.
react.html：
<html>
<head>
<link rel="stylesheet" href="react.css">
<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>
</head>
<body>
<div id="root"></div>
<script src="react.js" type="text/babel"></script>
</body>
</html>
react.js：
ReactDOM.render(<h1>Hello, World!</h1>, document.querySelector("#root"))
``` tried document.getElementById("root") as well
P粉3735968282024-01-11 09:12:30
To use @babel/standalone you also need to load it, otherwise type="text/babel" won't work.
<!-- 加载 Babel --> <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>