I want to modify my UWP app to operate slightly differently depending on the platform language. I know I can get the culture info when programming with C#, but this app is written with JavaScript.
I searched MSDN and looked through samples on gitHub but couldn't find any documentation or example indicating how to do it. I wonder if it's possible at all.
You can try to create a Windows Runtime component using C# then call this C# component from your JavaScript project. In this scenario, you can write a helper class to get the culture info in the C# Windows Runtime component using CultureInfo class, after that, you can reference this component and call the method of the C# class from your JS project to get culture info.
You can learn details from the offical document:
Walkthrough: Creating a Simple Windows Runtime component and calling it from JavaScript