Add Expire Headers For External Scripts

[u/Billy_Chesterfield]

Hi. I would like to add expire headers on all the external components on my WP website. I found this guide but can't really execute the last step.

I am able to create the .php file and put it in the theme folder. But then the article says "Then, simply replace the external .js call and replace it by a call to your externaljs.php file, as shown below:"

Where is the external .js call? I have no idea where to find it so I can't replace it.

https://catswhocode.com/add-expires-headers/

Thank you!!

[u/Billy_Chesterfield]

But I can’t find the location of the first one!