What is dependency injection in Angular?

Short answer: Dependency Injection (DI) is a design pattern in which objects receive their dependencies from an external source, not by creating them. Angular has a built-in DI system that allows services to be injected into components or other services.

Example code

constructor(private authService: AuthService) {} Real-Time Example: In an e-commerce app: Inject CartService into CartComponent to manage cart items.

Real-world example (ShopNest)

A shared CartService is injected into header and product pages so both see the same cart count.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.