Load a websites's remote script as a local script

A common problem I have when debugging a client site is being able to load a specific javascript file locally and leave other scripts from that remote host to be loaded from the remote address.

For example:

• I am debugging client.site.com which loads some scripts a.js, b.js, c.js, d.js amongst other resources.
• I need to debug file a.js, therefore I want to modify it locally and serve it locally.
• I could just change my /etc/hosts to point to local but then everything including the page itself would have to be downloaded and served locally.

• To avoid this I changed my ngnix config to put a little proxy-pass to redirect all requests back to the remote hose apart from that file, as shown below.

    server {
         listen 80;
         server_name client.site.com;
  
         location /a.js {
                 # your local server
                 proxy_pass http://localhost:80/;
                 proxy_set_header Host      $host;
                 proxy_set_header X-Real-IP $remote_addr;
         }
  
         location / {
                 # everything else back to the IP of client.site.com
                 proxy_pass http://<REMOTE_IP>/;
                 proxy_set_header Host      $host;
                 proxy_set_header X-Real-IP $remote_addr;
         }
    }
  

Perhaps there are simpler solutions, suggestions welcome!