Angular Interview Questions

Here’s a curated list of the top 20 most-asked Angular interview questions, covering a mix of basic, intermediate, and advanced topics:

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1. What is Angular?

Explain Angular as a TypeScript-based framework used for building web applications, focusing on features like modularity, components, and dependency injection.

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2. What is the architecture of Angular?

Discuss the structure of Angular applications, including Modules, Components, Templates, Services, Directives, and Routing.

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3. What is a Component in Angular?

Explain that a Component is the building block of an Angular application, containing logic (TypeScript), view (HTML), and styling (CSS).

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4. What are Directives in Angular?

Define Directives as classes used to modify DOM elements. Differentiate between:

• Structural directives (e.g., *ngIf, *ngFor)
• Attribute directives (e.g., [ngClass], [ngStyle]).

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5. What are the types of Data Binding in Angular?

Explain the four types:

1. Interpolation: {{expression}}
2. Property Binding: [property]="value"
3. Event Binding: (event)="handler()"
4. Two-way Binding: [(ngModel)]="value"

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6. What is Dependency Injection in Angular?

Describe how Angular provides services to components and other services using its built-in dependency injection mechanism.

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7. What are Angular Modules?

Discuss how NgModules group related components, directives, pipes, and services into cohesive blocks. Mention the @NgModule decorator.

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8. What is the difference between Template-driven and Reactive forms?

Highlight key differences:

• Template-driven forms: Simpler, uses HTML and directives like ngModel.
• Reactive forms: More robust, uses FormGroup and FormControl.

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9. What are Angular Lifecycle Hooks?

Discuss hooks like:

• ngOnInit()
• ngOnChanges()
• ngAfterViewInit()
• ngOnDestroy().

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10. What is Angular Routing?

Explain how Angular uses the RouterModule to define routes, navigate between views, and implement lazy loading for performance optimization.

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11. What is HttpClient in Angular?

Describe it as the Angular service for making HTTP requests. Mention its support for Observables and methods like get(), post(), put(), and delete().

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12. What are Pipes in Angular?

Explain how Pipes transform data in templates. Mention built-in pipes (| currency, | date, | async) and how to create custom pipes.

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13. What is Change Detection in Angular?

Explain how Angular’s Change Detection checks for updates in the application’s state and updates the DOM accordingly. Mention Zone.js.

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14. What is the difference between ViewChild and ContentChild?

• ViewChild: Accesses elements or components in the template.
• ContentChild: Accesses projected content inside <ng-content>.

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15. What are Angular Guards?

Discuss different guards (CanActivate, CanDeactivate, Resolve, CanLoad) and how they manage navigation and route access.

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16. What is the purpose of RxJS in Angular?

Explain how RxJS provides Observables for reactive programming, allowing you to handle asynchronous operations efficiently.

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17. What is the difference between JIT and AOT Compilation?

• JIT (Just-in-Time): Compiles code in the browser at runtime.
• AOT (Ahead-of-Time): Compiles code during the build process, leading to faster runtime.

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18. What is the difference between Subject, BehaviorSubject, and ReplaySubject?

Explain:

• Subject: Basic observable emitting data to subscribers.
• BehaviorSubject: Emits the latest value and initial value.
• ReplaySubject: Emits a specific number of last values to new subscribers.

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19. How do you implement Lazy Loading in Angular?

Discuss splitting the application into feature modules and using loadChildren in the route configuration.

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20. How do you handle error scenarios in Angular applications?

Talk about:

• Using HttpInterceptor for centralized error handling.
• Implementing catchError in RxJS.

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