How to change the response from the server?

Question

Nginx

Is it possible somehow to change the response from the server without making a redirect?
Let's say everything that starts with /api is sent to the backend

location /api {		
    rewrite ^/(.*)/$ /$1 permanent;
    proxy_pass https://127.0.0.1:9909;
  }

For everything else, specify the statics:

location / {	
    root C:/client;
  }

But what if the url is /articles or /auth? You need to somehow give the contents of the C:/client/index.html file, while not making a redirect. How to do it?
Would it be wrong to use error_page for this?

Answer 1

root C:/client;
rewrite ^/(articles|auth)$ /index.html;

Or

root C:/client;
location ~ ^/(articles|auth)$ {
    try_files /index.html =404;
}