Microsoft just released the new experience for SharePoint libraries and I know a lot of you built custom look and feel and/or components on top of the library ui. (I’m thinking in particular about ScriptLink actions)
You might be in a situation where the code you need to run will be different depending on the experience being used.
After a little bit of research, here is an example of solution.
https://gist.github.com/baywet/8fbb587023f306ee40bad00b3a23961a
Happy coding!