Why cannot access static files of grafana service?

I launch Grafana using official docker following the docs running grafana behind proxy and installing grafana using docker, with command:

docker run -itd -p 3000:3000 
-v ~/grafana_storage:/var/lib/grafana 
-e "GF_SERVER_DOMAIN=www.jijunxu.cn" 
-e "GF_SERVER_ROOT_URL=https://www.jijunxu.cn/grafana/" 
--rm grafana/grafana

and nginx.conf:

location /grafana/
    proxy_pass http://localhost:3000/;

but I got this page when accessing https://www.jijunxu.cn/grafana/ saying:

If you're seeing this Grafana has failed to load its application files 

1. This could be caused by your reverse proxy settings.

2. If you host grafana under subpath make sure your grafana.ini root_url setting includes subpath

3. If you have a local dev build make sure you build frontend using: npm run dev, npm run watch, or npm run build

4. Sometimes restarting grafana-server can help

and 404 on CSS and JS files. I have tried all those methods but it remains the same. So is there any problem with my nginx.conf or docker command?

Source: StackOverflow