script标签引入react环境三个必须cdn文件

<script src="https://cdn.bootcss.com/react/16.8.6/umd/react.development.js"></script>

<script src="https://cdn.bootcss.com/react-dom/16.8.6/umd/react-dom.development.js"></script>

<script src="https://cdn.bootcss.com/babel-standalone/6.26.0/babel.js"></script>