I need to test something on a test site from my local to see that a url is check in the code is working

I need to test whether some javascript I wrote that checks the url on a production site will work before I deploy it there. The url check is pretty basic.

window.location.hostname === "prodlogin.site.com"

But the test url I have is different than production and I don't want to add all our test, dev, uat, staging login links to the production assets.

The url that the test site is on is testlogin.site.com

How would I go about testing this locally on my machine. I need the url to say prodlogin.site.com but I need the files to come from testlogin.site.com.

Host? Apache config? .htaccess?