There are many cross-site solutions, the common ones are JSONP, proxy forwarding, and the new feature of HTLM5's Allow Origin that allows cross-site access.

In your case, it is recommended to set up a proxy in Ngingx of the website and forward it to the website backend. The configuration is probably like this:

upstream backend {
    server backend1.example.com:8080;
}

server {
    location /api {
        proxy_pass http://backend;
    }
}

On the front-end page, the address accessed through ajax is: http://www.example.com/api/xxx

Different ports are inherently different sites, and sites are cross-domain! By separating the front-end and back-end, the website can be more secure and can be maintained separately. I don’t think it is necessary to use the front-end to cross-domain requests to the back-end. This will expose the back-end, and the program design should not retrieve data across domains through the front-end. Bar! Unless your database is a file database such as Access or SQLite, then it is a design problem. Requesting data only requires a data connection. No need to cross domains.