The topic of dependency wiring is certainly one of the most opinionated in software engineering, but in this chapter, we tried to keep the analysis as factual as possible to give an objective overview of the most important wiring patterns. We cleared some of the most common doubts around Singletons and instances in Node.js, and we learned how to connect modules using hardcoded dependencies, DI, and service locators. We practiced each technique using the authentication server as a playground, allowing us to identify the pros and cons of each approach.
In the second part of the chapter, we learned how an application can support plugins, but most importantly, how we can wire those plugins into the main application. We applied the same techniques presented in the first part of the chapter but analyzed them from another perspective. We discovered how important it can be for a plugin to have access to the right services of the main application and how much this can impact its capabilities...