Ngnix dynamic reverse proxy for multiple domain names.How to do it?

Question

Referring to the following three websites, you can input any website in the input box, such as: enter www.google.com, search results, click on any content, and it will be reverse proxied. What is the technical approach?

1. https://www.vpnbook.com/webproxy/

2. https://plainproxies.com/resources/free-web-proxy

3. https://www.proxysite.com/

Now I only know the one-to-one reverse proxy mode, that is, reverse proxy from one domain name to another domain name. Now I can only reverse proxy www.google.com, and the hyperlinks of search results should also be reverse proxy