Component Based UI

The basic idea behind a component based UI is that instead of separating your code based on the technologies used to create it (separation of concerns) it's much better practice to instead separate your code based on the component it is being used to create.

In this new way of doing things if you have a component such as a form. All of the HTML, CSS, and JS that relate to that form should be handled in one file. This gives you quite a few advantages. Whenever you need to make changes to that component it becomes incredibly easy because you only need to go to one file and change it. It also has the advantage of allowing you to reuse components all over the place.