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Angular MCQ With Answers

41 practice questions · Last updated on Aug 25, 2026

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Angular interviews lean heavily on architecture, because Angular is chosen for large applications. Expect questions on dependency injection and injector hierarchies, how change detection works and what OnPush changes, the RxJS flattening operators and when each is correct, reactive forms, route guards and lazy loading, and how to avoid subscription memory leaks. Signals and standalone components increasingly appear as well. The questions below cover the framework mechanics and the performance decisions that follow from them.

Angular MCQ

1.What is Angular?

2.What does the @Injectable({ providedIn: 'root' }) decorator do?

3.When does a component with ChangeDetectionStrategy.OnPush get checked?

4.Which RxJS operator cancels the previous inner observable when a new value arrives?

5.Which RxJS operator ignores new values while an inner observable is still running?

6.In which lifecycle hook should data fetching be initiated?

7.Which lifecycle hook is used to clean up subscriptions?

8.Which is the cleanest way to consume an observable in a template?

9.What is the main advantage of reactive forms over template-driven forms?

11.What is the purpose of an HTTP interceptor?

12.Why must an interceptor clone the request before modifying it?

13.What does the trackBy function on ngFor do?

14.What is an Angular signal?

15.What is the difference between a structural and an attribute directive?

16.What does the ng-content element do?

17.Which module method registers application-level routes?

18.How is lazy loading configured for a route?

19.What is the difference between a pure and an impure pipe?

20.What does the @Input() decorator do?

22.What does the Angular CLI command 'ng build --configuration production' enable?

23.Which error commonly appears when a bound value is modified inside ngAfterViewInit in development mode?

24.What is the purpose of an InjectionToken?

25.When does Angular create a separate instance of a service provided in root?

26.What does the HttpClient return by default?

27.Which is the correct way to activate a non-default relationship between two routes' data?

28.What is the difference between BehaviorSubject and Subject?

29.Which decorator marks a class as an Angular component?

30.What is the earliest lifecycle hook where a @ViewChild reference is guaranteed to be available?

31.Which of these correctly binds a property in an Angular template?

32.What does the Angular router's ActivatedRoute paramMap provide?

33.Which technique reduces the initial bundle size most effectively in a large Angular application?

34.What is the purpose of the async pipe with OnPush change detection?

36.What is a common cause of a memory leak in an Angular component?

37.What does the Angular AOT compiler do?

39.What is a standalone component in modern Angular?

40.Why should a function call be avoided in an Angular template expression?

41.What does the Angular dependency injection hierarchy determine?

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