Angular is a full, opinionated framework, so its interviews test how well you understand its architecture: components and modules, dependency injection, data binding, RxJS, and change detection. Knowing these structural concepts matters more than memorizing API names. Here are the Angular interview questions that actually get asked, with answers. (See also our TypeScript guide.)
Components & architecture
- Components, modules, and services — how they fit together.
- Data binding types — interpolation, property, event, and two-way.
- What is dependency injection and why does Angular use it?
- Component lifecycle hooks (ngOnInit, ngOnChanges, ngOnDestroy…).
- @Input and @Output; component communication.
RxJS & async
- What is an Observable, and Observable vs Promise?
- Common operators — map, filter, switchMap, mergeMap.
- The async pipe; subscribing and unsubscribing (memory leaks).
- Subjects vs BehaviorSubjects.
Change detection & performance
- How does Angular's change detection work?
- Default vs OnPush change detection strategy.
- What causes performance issues and how do you fix them?
- Lazy loading modules; AOT vs JIT compilation.
How to prepare
Angular rounds mix concepts with "how would you fix this" discussions, all verbal. Practise explaining DI and change detection out loud. Greenroom runs spoken technical interviews that follow up on your reasoning. Pair it with our TypeScript and frontend guides.
Frequently asked questions
What are the most common Angular interview questions?
Common Angular questions cover components, modules and services, data binding types, dependency injection, lifecycle hooks, component communication (@Input/@Output), RxJS (Observables vs Promises, operators like switchMap and mergeMap, the async pipe, Subjects vs BehaviorSubjects), and change detection (default vs OnPush), plus performance topics like lazy loading and AOT vs JIT.
What is dependency injection in Angular?
Dependency injection is a design pattern where Angular provides a class's dependencies (like services) from the outside rather than the class creating them itself. You declare dependencies in the constructor and Angular's injector supplies registered instances. This improves testability, reuse and modularity, and lets you control whether a service is a singleton or scoped to a component.
How does change detection work in Angular?
Angular's change detection checks component data bindings and updates the DOM when data changes, triggered by events, HTTP responses and timers via Zone.js. The default strategy checks the whole component tree, while OnPush only checks a component when its inputs change by reference or an event fires within it, which significantly improves performance in large apps.
How should I prepare for an Angular interview?
Focus on the framework's structure — dependency injection, change detection, RxJS streams and lifecycle hooks — rather than memorizing API names, since understanding why concepts exist is what's tested. Practise explaining things like why OnPush improves performance out loud with a voice-based mock interview, because Angular rounds mix concepts with verbal debugging discussions.