- React – Props
Props are the arguments a component takes. Destructuring them in the signature, typing them with TypeScript, default values, the children prop, and passing functions down so a child can talk back to its parent. Plus the rule that explains half of all React bugs: props are read-only.
- Spring Boot – Dependency Injection
Inversion of control in the only form that matters day to day: constructor injection. Why field injection with @Autowired is the wrong default, how Lombok's @RequiredArgsConstructor removes the boilerplate that made people reach for it, and how to break a circular dependency instead of papering over it with @Lazy.
- Angular – Content Projection and ng-template
Writing a component that wraps content it does not own. Single-slot and multi-slot `<ng-content>`, selecting what lands where, `<ng-template>` and `<ng-container>` and the difference between them, and `ngTemplateOutlet` for the cases where a slot is not flexible enough.
- Docker – Images, Layers and Tags
An image is a stack of read-only layers and a container is a thin writable layer on top — which explains sharing, caching, image size and why editing a file in a running container changes nothing permanent. Reading `docker history`, what a tag really is, and why a digest is the only thing that pins an image.
- Java Variables
A variable is a named box that holds a value of a declared type. That definition sounds trivial and it is, but three things about variables in Java are not: the type is fixed, where you declare one decides how long it lives, and Java has three distinct kinds that behave differently. Declaring and…