nginx-several questions about location pattern

I checked a lot of information but couldn’t figure out a few questions.

The first question, if my location configuration is like this:

location /doc {
    alias /home/user/doc;
}

Then when I visit http://localhost/doc/a.html, nginx actually reads /home/usr/doc/a.html. If I visit http://localhost /docs/a.html or even http://localhost/docsioajsfopajowejfasd So which file will nginx actually try to read?

Second question, if I configure doc as a server and then reverse proxy.

server {
    listen 8000;
    server_name doc;
    root /home/user/doc;
    
    index index.html index.htm index.nginx-debian.html;

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        try_files $uri $uri/ =404;
    }
}

Configure it like this on the main server:

server {
    listen 80;
    ....
    location /doc {
        proxy_pass http://localhost:8000/;
    }
    }

When accessing http://localhost/doc/ when configured in this way, if the index file references a static file, the static file will become 404, and the browser will try to obtain http://localhost/js/xxx.js instead of http://localhost/doc/js/xxx.js, if you add / after pattern it becomes

location /doc/ {
            proxy_pass http://localhost:8000/;
        }

There is no problem, but if it is the location configuration in the first question, the browser will correctly find http://localhost/doc/js/xxx.js. This makes me very confused. What is the impact of adding / at the end? Why do alias and proxy_pass have different results?

Reply content:

I checked a lot of information but couldn’t figure out a few questions.

The first question, if my location configuration is like this:

location /doc {
    alias /home/user/doc;
}

Then when I visit http://localhost/doc/a.html, nginx actually reads /home/usr/doc/a.html. If I visit http://localhost /docs/a.html or even http://localhost/docsioajsfopajowejfasd So which file will nginx actually try to read?

Second question, if I configure doc as a server and then reverse proxy.

server {
    listen 8000;
    server_name doc;
    root /home/user/doc;
    
    index index.html index.htm index.nginx-debian.html;

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        try_files $uri $uri/ =404;
    }
}

Configure it like this on the main server:

server {
    listen 80;
    ....
    location /doc {
        proxy_pass http://localhost:8000/;
    }
    }

When accessing http://localhost/doc/ when configured in this way, if the index file references a static file, the static file will become 404, and the browser will try to obtain http://localhost/js/xxx.js instead of http://localhost/doc/js/xxx.js, if you add / after pattern it becomes

location /doc/ {
            proxy_pass http://localhost:8000/;
        }

There is no problem, but if it is the location configuration in the first question, the browser will correctly find http://localhost/doc/js/xxx.js. This makes me very confused. What is the impact of adding / at the end? Why do alias and proxy_pass have different results?