When learning Angular, Spring, and Node.js, I often came across terms like SOLID, Dependency Injection (DI), Inversion of Control (IoC), IoC Container, and Composition.
At first, these concepts can feel like they are all the same thing. They are not.
The key realization is:
SOLID is about how we design software. Composition is about how we build larger systems from smaller pieces. Dependency Injection is a technique for providing those pieces. IoC containers automate that process.
Understanding this relationship makes Angular, Spring, and Node.js architectures much easier to reason about.
