These are our Drupal 9 books:
Back-End development in Drupal 9 refers to the programming of modules and components that allow extending the functionality of the system. It is mainly object-oriented PHP programming, although we will also see other technologies needed during the development of a web project.
Front-End development in Drupal 9 encompasses all interface-related technologies that run in the web browser. We can group these technologies into three languages, HTML, CSS and JavaScript. Although these technologies are used as a base, we will see that there are other more advanced solutions that facilitate Front-End programming. For example, we will use SASS for CSS generation and JavaScript libraries such as jQuery or VueJS.