From studying object-oriented programming in university, it was drilled into us how different classes separate concerns, and how different layers of an application should serve different purposes e.g. you can’t have database access procedures in a class that deals with the front end page.
But, lo and behold. Something else has been advised from the secret organisation that designs international best practices that everyone should conform to without questioning it.
When developing a web user interface, the html should determine the structure, the stylesheet should determine how the page looks, and javascript should determine the behaviour. These should be separated.
This means that there shouldn’t be any styling beyond the basic structure in the html. There shouldn’t be any click actions in the html.
Truly revolutionary. Changed my life.