Social Media Dashboard | SCSS & Vanilla JS with Local Storage

I have added a feature where your theme preference gets saved to the Local Storage where the theme stays dark upon page refresh. However, I couldn't quite get how to complete the following requirement of the challenge "Toggle color theme to their preference".

Wasn't sure whether to use a prefers-color-scheme media query on the variables decaled in body.dark or check for it in the JavaScript.

Would appreciate any insight or tips on how to check for the systems color scheme preference and apply it to my code.