Top 30 Angular Interview Questions and Answers (Part 3)

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If you’re preparing for an Angular interview, diving deeper into advanced topics and edge cases can give you an edge.

Basic Questions
  • 1. What is structural directive in Angular?

    A structural directive changes the DOM layout by adding or removing elements, e.g., *ngIf and *ngFor.

  • 2. How does Angular handle attribute binding?

    Attribute binding uses [attr] syntax to dynamically set attributes on DOM elements, e.g., [attr.aria-label]="label".

  • 3. What is Angular’s CLI schematics?

    CLI schematics automate tasks such as generating components, services, and modules using predefined templates.

  • 4. What is the purpose of TestBed in Angular?

    TestBed is used in Angular unit testing to create and configure components and services in a test environment.

  • 5. What is a provider in Angular?

    A provider defines how a service or value is created and injected. Providers can be specified in modules, components, or services.

  • 6. What is the difference between ng-template and ng-container?

    • ng-template: Defines a template that is rendered dynamically.
    • ng-container: Groups elements without adding a new DOM element.

  • 7. What are async pipes in Angular?

    An async pipe subscribes to an observable or promise and automatically handles unsubscribing when the component is destroyed.

  • 8. How does Angular handle multiple modules?

    Multiple modules are used to separate features in large applications, with shared and feature modules managing shared resources and functionalities.

  • 9. What is a shared module in Angular?

    A shared module contains reusable components, directives, and pipes that can be imported into other feature modules.

  • 10. What is Angular’s default change detection strategy?

    The default strategy checks all components in the component tree for changes during each change detection cycle.

Intermediate Questions
  • 11. What are Angular zones?

    Zones in Angular help track asynchronous operations like HTTP requests, user events, and timers, triggering change detection when necessary.

  • 12. How do you create custom validators in Angular?

    Create a function that implements the ValidatorFn or AsyncValidatorFn interface, and apply it to form controls or groups.

  • 13. How does Angular handle nested routes?

    Nested routes are configured in the children property of a route definition, enabling multi-level navigation.

  • 14. What is a host listener in Angular?

    @HostListener is a decorator that listens to events on the host element and executes a method when the event occurs.

  • 15. How do you detect and prevent memory leaks in Angular?

    Prevent memory leaks by unsubscribing from observables, using async pipes, and cleaning up event listeners in ngOnDestroy.

  • 16. What is Angular’s HttpInterceptor?

    An HttpInterceptor modifies HTTP requests and responses globally, e.g., adding headers or handling errors.

  • 17. How do you handle dynamic forms in Angular?

    Dynamic forms are created programmatically using FormGroup and FormControl instances.

  • 18. What is differential loading in Angular?

    Differential loading generates two bundles: one for modern browsers and another for older browsers, optimizing application performance.

  • 19. What is a singleton service in Angular?

    A singleton service is instantiated once per application and shared across all components and modules. This is achieved by providing it in the root module or using providedIn: 'root'.

  • 20. What is a polyfill in Angular?

    Polyfills enable Angular to support older browsers by emulating missing features (e.g., ES6+ features).

Advanced Questions
  • 21. What is Angular’s NgZone?

    NgZone is a service used to manually trigger or disable Angular’s automatic change detection.

  • 22. How do you optimize large Angular applications?

    Use lazy loading, AOT compilation, OnPush change detection, tree-shaking, and service workers for optimization.

  • 23. What is a meta reducer in NgRx?

    A meta reducer is a higher-order reducer that wraps other reducers to apply global logic, such as logging or resetting the state.

  • 24. How does Angular handle security?

    Angular provides built-in mechanisms like DOM sanitization, XSS protection, and HttpClient to prevent security vulnerabilities.

  • 25. What is the role of ContentChild and ContentChildren?

    They query elements projected into a component using ng-content and provide references to them.

  • 26. What are multi-providers in Angular?

    Multi-providers allow multiple providers for the same token, creating an array of values instead of overwriting the previous provider.

  • 27. What is preloading in Angular routing?

    Preloading loads lazy-loaded modules in the background after the application is bootstrapped to improve performance.

  • 28. How does Angular’s rendering engine work?

    The Ivy rendering engine converts templates into highly optimized JavaScript instructions for better runtime performance.

  • 29. What is a route resolver?

    A route resolver fetches data before activating a route, ensuring the required data is available for the component.

  • 30. What are hybrid apps in Angular?

    Hybrid apps combine AngularJS and Angular components in the same application, enabling gradual migration to Angular.

Conclusion

These 30 Angular questions delve into advanced concepts, helping you stand out during interviews. Be sure to back up your answers with real-world examples and hands-on experience.

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