前言
Nuxt 官方文档：asyncData is called every time before loading the page component and is only available for such. It will be called server-side once (on the first request to the Nuxt app) and client-side when navigating to further routes.
啥意思呢，asyncData 并不是每次都从服务端渲染，只有当页面刷新时才从服务端渲染，而在客户端点击链接跳转时并不从服务端渲染，而是和标准 Vue SAP（单页面） 应用一样，从客户端进行渲染。
