For me, the concept of directives from the first version of Angular changed the game in frontend UI frameworks. This was the first time that I felt that there was a simple yet powerful concept that allowed the creation of reusable UI components. Directives could communicate with DOM events or messaging services. They allowed you to follow the principle of composition, and you could nest directives and create larger directives that solely consisted of smaller directives arranged together. Actually, directives were a very nice implementation of components for the browser.

In this section, we'll look into the component-based architecture of Angular and how the things we've learned about components will fit into Angular.

As an early adopter of Angular and while talking to other people about it, I got frequently asked what the biggest difference is to the first version. My answer to this question was always the same. Everything is a component:

For me, this paradigm shift was the most relevant change that both simplified and enriched the framework. Of course, there are a lot of other changes with Angular. However, as an advocate of component-based user interfaces, I've found that this change is the most interesting one. Of course, this change also came with a lot of architectural changes.

Angular supports the idea of looking at the user interface holistically and fosters composition with components. However, the biggest difference to its first version is that now, your pages are no longer global views; they are simply components that are assembled from other components. If you've been following this chapter, you'll notice that this is exactly what a holistic approach to user interfaces demands. No more pages, but systems of components.