How do I pass the shop's permanent domain to my theme app extension javascript asset?

[Knert]

My app is currently held up in review because I need to create a theme app extension instead of using a script tag for 2.0 themes. 

Some notes:

1. My app is a standalone app.
2. I've added code to my login process to detect a 2.0 theme and not install the script tag. 
3. I have created a theme-app-extension on my app, included my javascript file in the theme-app-extension asset/ folder, and published it to my development store successfully.
4. How do I pass the shop's permanent domain to my theme app extension javascript asset?

I've been working on this for a couple of days now and can't figure it out. I appreciate any help. Thanks!

[DivinityWebS]

You will get shop domain in Shopify.shop in JavaScript asset