Get domain name of static file using javascript

One of my domains have inclusions of multiple cdn's. I need to dynamically include a file based on the hostname of one of the cdn's.

host name : www.example.com

cdn1.example.com has 2 files cdn-js-1.js and cdn-js-2.js

cdn-js-1.js has a code to call to cdn-js-2.js conditionally from cdn1.example.com domain (NOT www.example.com)