今天用create-react-app my-app，看到下面的提示：
A template was not provided. This is likely because you‘re using an outdated version of create-react-app.
Please note that global installs of create-react-app are no longer supported.
在package.json中你会看到react-scripts升级到了3.3.0，它不再支持全局安装CRA（create-react-app)。
查了一些资料，朋友们都说用npx create-react-app my-app可以，经过我不断试错，才发现前提是一定要先卸载全局CRA才能成功！
所以，卸载全局CRA
npm uninstall -g create-react-app
但是发现卸不掉CRA，因为下面的command还可以拿到它的版本号：
create-react-app -V
->3.0.1
怎么办嘞？那就手动删除吧，执行下面的command:
which create-react-app
->/usr/local/bin/create-react-app
rm -rf /usr/local/bin/create-react-app
create-react-app -V
-bash: /usr/local/bin/create-react-app: No such file or directory
删除成功！
最后用npx就快速生成react项目，运行OK
npx create-react-app my-app