Can someone tell me why this doesn't work locally using cdn links

<h1>Hello React!</h1>, document.getElementById('root'))

<script crossorigin src="[url=https://unpkg.com/react@16/umd/react.production.min.js"></script>]https://unpkg.com/react%4016/u ... gt%3B[/url]

  <script crossorigin src="[url=https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"></script>]https://unpkg.com/react-dom%40 ... gt%3B[/url]