Fluid adaptive with custom js code

Friends, hello everyone! I have a problem. I need to write one JS function, which would take into webflow the value of the size of elements and font, that is, as if listening to them and based on this I would like to do fluid adaptive, so as not to use third-party services and so on. How to do it!? That is, I need to hang a listener on all inputs with sizes in webflow. Thanks!

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@Takov_Web - can you provide an example or clearer explanation of what you are looking for?