今天准备把一个异步加载的组件用Suspense，结果似乎不行。
报错如下：

ReactDOMServer does not yet support Suspense.

后来又搜到一个帖子，看来是确定了：
https://spectrum.chat/next-js/general/suspense-support~f83c5c32-cb4d-419e-ba3d-f08948e63584

1. It is rendered once on the server - it is the root of your app
2. App's getInitialProps is called before anything else - even before getInitialProps in _document.js
3. It is created and mounted ONLY ONCE on the client - when the page first loads. Thereafter, on page navigation, App.getInitialProps is called before each page, and then its render function is called, to render the incoming page.

- 阅读剩余部分 -

首先，Next.js是个好学校，啊不，是个好框架；
其次，Next.js的文档也不算烂，但确实有点简陋，好多都是undocumented。

Next.js有个feature叫做file-system routing:

By default, Next will serve each file in /pages under a pathname matching the filename (eg, /pages/some-file.js is served at site.com/some-file.

你可以设置一个option来turn it off:

// next.config.js
module.exports = {
  useFileSystemPublicRoutes: false,
}

我今天谈论的重点是这个问题：当我在Components/SomeComponenet.jsx里使用router（不论是useRouter还是withRouter），都会报错，错误信息这样的：

- 阅读剩余部分 -

useRouter用在functional component里；
withRouter用在class component里。