Angular Interview Preparation

• Angular Basics and Core Angular Concepts

1. Why were client-side frameworks like Angular introduced?

• Client-side frameworks like Angular were introduced to simplify the development of dynamic single-page applications (SPAs). They address challenges like:

  • Managing complex UIs.

  • Handling asynchronous communication with back-end services.

  • Improving user experience by providing faster load times and seamless navigation.

  • Organizing code using components and modules, which increases reusability and maintainability.

2. What are Single Page Applications (SPA)?

• SPAs are web applications that load a single HTML page and dynamically update the page as the user interacts with the app. This provides a seamless, fast user experience without full page reloads.

3. What is Angular Framework?

• Angular is a platform and framework for building client-side applications using HTML, CSS, and TypeScript. It is a component-based framework that allows developers to build scalable, modular applications, especially suited for single-page applications (SPAs).

4. What is TypeScript, and why is it used in Angular?

• TypeScript is a strongly-typed, object-oriented programming language that builds on JavaScript by adding optional static types. TypeScript is a superset of JavaScript that adds static typing and other features like interfaces, generics, and decorators. It’s used in Angular because it:

  • It provides type-checking at compile time, improving code quality and debugging.

  • Makes code easier to understand and debug.

  • Offers better tooling support (e.g., auto-completion, refactoring).

  • Helps catch errors during development.

  • Improves maintainability of large-scale applications.

5. What are the advantages of Angular over other frameworks?

• TypeScript support (static typing).

• Strong MVC pattern support.

• Modular architecture with components and modules.

• Built-in dependency injection for improved testability and scalability.

• A powerful CLI for scaffolding and managing Angular projects.

• RxJS integration for managing asynchronous data streams.

6. What is the difference between AngularJS and Angular?

• AngularJS refers to Angular 1.x, which is a JavaScript-based framework, while Angular refers to versions 2 and above, which are TypeScript-based and offer better performance, modularity, and mobile support.

• AngularJS has a scope-based architecture, while Angular uses component-based architecture.

• AngularJS uses two-way data binding, while Angular has a more refined one-way data flow with improved change detection.

7. How does an Angular application work?

• Angular uses the Component-Driven Architecture and the Angular Router to load different views dynamically, offering the experience of a single-page app.

8. What are Angular components, modules, and services?

• An Angular application is composed of:

  • Components: The basic building blocks of Angular apps, which control views and encapsulate the UI and behavior.

  • Modules: Containers that group related components, services, directives, and pipes. Every Angular app has at least one module, typically called the AppModule.

  • Services: Centralize common logic or tasks (like API calls), often injected into components via dependency injection. Used to handle business logic, data fetching, and communication between components.

9. What are the key components of Angular?

• Modules: Organizational structure.

• Components: Define the UI and handle user interaction.

• Templates: Bind data and define the HTML structure of a view.

• Services: Provide data and logic to components.

• Directives: Alter DOM elements.

• Pipes: Transform data in templates.

10. Explain the Angular architecture

• Angular Architecture consists of:

  • Modules: Organize an application into cohesive blocks.

  • Components: Define the UI logic and layout.

  • Templates: HTML views associated with components.

  • Metadata: Adds extra information to classes via decorators.

  • Services: Business logic and data handling.

  • Dependency Injection: Supplies the required dependencies to components/services.

  • Directives & Pipes: Transform DOM elements or data.

11. What are templates in Angular?

• Templates in Angular are written in HTML and define the view. They can also bind data using data binding and Angular directives to dynamically render content based on conditions.

12. What are lifecycle hooks? Explain a few.

• Lifecycle hooks are events in an Angular component’s life, such as creation, rendering, and destruction. Common ones include:

  • ngOnInit(): Called after the component is initialized.

  • ngOnDestroy(): Called before the component is destroyed.

  • ngOnChanges(): Responds to changes in the input properties.

13. What are decorators and their types in Angular?

• Decorators are special functions that attach metadata to classes, methods, or properties. Common types:

  • @Component: Declares a component.

  • @NgModule: Declares an Angular module.

  • @Injectable: Declares a service that can be injected.

  • @Input(): Marks a property as an input property for a component.

  • @Output(): Marks a property as an output event emitter.

14. What is the Component Decorator in Angular?

The Component Decorator is a metadata annotation that tells Angular that a class is a component. It provides details such as the selector, template URL, and styles.

@Component({

  selector: 'app-hero',

  templateUrl: './hero.component.html',

  styleUrls: ['./hero.component.css']

})

15. What is a bootstrapping module?

• The bootstrapping module is the module that is used to launch or bootstrap the Angular application. Typically, this is the AppModule and is listed in the main.ts file:
  typescript
  Copy code
  platformBrowserDynamic().bootstrapModule(AppModule);

• Directives

  1. What are directives in Angular?

  2. What are the differences between a Component and a Directive?

  3. What are built-in directives?

  4. What are attribute and structural directives?

  5. What are attribute directives? Provide examples.

  6. Explain structural directives.

• Pipes

  1. What are pipes in angular, and how do you use them? Give an example.

  2. What is a pure vs impure pipe? What is the difference between pure and impure pipes?

  3. How do you create a custom pipe? Give an example.

  4. How do you create custom directives?

  5. What is a custom pipe? Provide an example.

  6. What is the PipeTransform interface?

  7. How do you chain pipes?

  8. What is a parameterized pipe?

• Data Binding

  1. What is data binding in Angular?

  2. Explain two-way data binding.

  3. What is string interpolation in Angular?

  4. Explain property binding vs. event binding.

• Component Communication

  1. How do you communicate between parent and child components using @Input and @Output?

  2. How do you transfer data between non-related components?

  3. Explain ViewChild and ViewChildren decorators.

  4. What is content projection? Provide an example.

• Data Binding & Component Communication

  1. What is data binding in Angular?

  2. What is two-way data binding?

  3. How do you share data between components? (Parent-Child, Child-Parent, Sibling Components)

  4. What are lifecycle hooks for component communication (e.g., ngOnInit, ngDoCheck)?

  5. What is ViewChild, ViewChildren, and ContentChild?

  6. What is content projection in Angular?

• Lifecycle Hooks

  1. What are Angular lifecycle hooks?

  2. Explain commonly used lifecycle hooks such as ngOnInit, ngOnChanges, ngDoCheck, ngAfterViewInit, and ngOnDestroy.

  3. How does Angular handle change detection?

• Change Detection

  1. What is change detection in Angular, and how does it work?

  2. What are the differences between the default and onPush change detection strategies?

  3. How can you manually trigger change detection?

  4. What are the different ways to trigger Change Detection?

• Dependency Injection

  1. What is Dependency Injection (DI) in Angular?

  2. How are services injected in Angular?

  3. Explain the use of resolution modifiers such as @Optional, @Self, and @SkipSelf DI?

  4. How is the dependency hierarchy formed?

  5. What are providers in Angular? (useValue, useClass, useFactory)

  6. What is the @Injectable decorator?

  7. What is providedIn?

  8. How do you create a singleton service?

• Routing and Navigation

  1. What is Angular Router?

  2. Explain routing with eager loading and lazy loading. Give Examples

  3. How does lazy loading differ in standalone and non-standalone components?

  4. How do you define routes, and what is a Wildcard route?

  5. What are route guards like CanActivate, CanDeactivate, and Resolve?

  6. What is the purpose of the base href tag?

  7. What are router outlets and router links?

  8. What is activated route service?

  9. What are Route Guards? Explain CanActivate, CanActivateChild, CanLoad, CanDeactivate, and Resolve.

  10. How do you configure routes in Angular?

  11. What is a wildcard route?

  12. What are router events?

  13. Explain nested and child routes.

  14. What is a routed entry component?

• Forms in Angular

  1. What are template-driven forms and reactive forms in Angular?

  2. What are template-driven forms?

  3. What are reactive forms? Differences from template-driven forms.

  4. Explain form validation (built-in and custom validators).

  5. How do you implement dynamic forms in Angular?

  6. Explain the difference between setValue and patchValue.

  7. What are validators in Angular forms? (Built-in and custom)

  8. What are form control states (pristine, dirty, touched, untouched)?

  9. How do you reset forms in Angular?

  10. How do you handle dynamic forms?

  11. What is FormBuilder?

• HTTP Client, RxJS and Observables

  • What is HttpClient, and how do you use it in Angular?

  • How do you handle HTTP requests with observables?

  • How do you perform error handling using catchError?

  • What are HTTP interceptors, and how are they used?

  • Explain how to perform GET, POST, PUT, DELETE requests using HttpClient.

  • What are HTTP interceptors, and what are their applications?

  • How do you handle errors in HTTP calls?

  • What are observables and observers in Angular?

  • What is RxJS? Explain key operators like map, catchError, switchMap, mergeMap, concatMap.

  • What is forkJoin in RxJS?

  • How do you share an observable result across multiple subscribers? (e.g., shareReplay)

  • Explain the difference between observables and promises.

  • What is HttpInterceptor, and how do you use it for an entire application?

  • What is RxJS, and how does Angular use it?

  • What are observables and promises, and how are they different?

  • Explain map, switchMap, mergeMap, and concatMap operators.

  • What is the purpose of the forkJoin operator?

  • What are Subjects in RxJS?

12. Testing

• How do you write unit tests for Angular components and services?

• What is TestBed in Angular testing?

• Explain Protractor and its use in end-to-end (E2E) testing.

Testing in Angular

1. What is TestBed in Angular?

2. How do you test components and services?

3. What is Protractor?

4. How do you create test cases for form validation?

34. HTTP Testing

• How do you test HTTP calls in Angular?

• What is HttpTestingController, and how is it used?

• How do you mock HTTP requests in unit tests?

Additional Angular Interview Topics and Questions:

20. Services and Providers

• How do you define and inject a service in Angular?

• What is the difference between providing services in root and component level?

• What are multi-providers in Angular?

13. Performance and Optimization

• How do you optimize Angular applications (lazy loading, change detection strategies)?

• What is differential loading in Angular CLI?

14. Miscellaneous

• How do you add Bootstrap to an Angular application?

• What is the purpose of APP_INITIALIZER?

• What are Angular Elements and how do they work?

15. Angular CLI

• What is Angular CLI, and why is it used?

• What are some common Angular CLI commands?

• How do you create and serve a new Angular project using Angular CLI?

• How can you add custom configurations in angular.json?

16. Angular Animations

• What are Angular animations, and how do you implement them?

• Explain how to use the trigger, state, transition, and animate functions.

• How can animations improve the user experience?

17. Internationalization (i18n)

• What is i18n in Angular?

• How do you implement internationalization in an Angular application?

• How do you handle language translation in Angular?

18. Angular Material

• What is Angular Material, and how do you install and use it?

• What are some common Angular Material components?

• How do you customize Angular Material themes?

21. Error Handling and Debugging

• How do you handle errors in Angular applications?

• What is the use of ErrorHandler in Angular?

• How do you debug Angular applications effectively (e.g., using Augury, Chrome DevTools)?

22. Zone.js

• What is Zone.js, and what role does it play in Angular?

• How does Zone.js work in Angular?

• How does Angular use Zones to manage asynchronous operations?

• Can you disable Zone.js in Angular? What would be the impact?

23. SSR (Server-Side Rendering)

• What is Server-Side Rendering (SSR), and why is it used?

• What is Angular Universal, and how do you set it up?

• What are the benefits and challenges of SSR in Angular applications?

24. NgModules

• What are NgModules, and how are they used in Angular?

• What is the difference between root, feature, and shared modules?

• How do you lazy load modules in Angular?

25. Tree Shaking

• What is tree shaking in Angular?

• How does Angular use tree shaking to optimize the application size?

26. Custom Decorators

• How do you create a custom decorator in Angular?

• What is the purpose of using custom decorators?

27. State Management

• What are some common state management libraries used with Angular (e.g., NgRx, Akita)?

• How do you manage state in an Angular application without external libraries?

• Explain the key concepts of NgRx: actions, reducers, selectors, effects.

28. Lazy Loading

• What is lazy loading in Angular, and how does it help with performance?

• How do you implement lazy loading of modules?

• How do you preload lazy-loaded modules?

29. Standalone Components

• What are standalone components in Angular?

• How do standalone components differ from traditional Angular components?

• What are the advantages of using standalone components?

30. Environment Configuration

• How do you manage environment-specific configurations in Angular?

• How do you differentiate between development and production environments?

• What are environment variables, and how do you configure them in Angular?

31. Content Projection

• What is content projection in Angular?

• How do you use ng-content for content projection?

• Explain multi-slot content projection.

32. Web Workers

• What are web workers in Angular, and how do they improve performance?

• How do you implement web workers in Angular?

33. PWAs (Progressive Web Apps)

• What is a Progressive Web App (PWA)?

• How do you convert an Angular application into a PWA?

• What are the benefits of using PWAs?

35. Custom Validators

• How do you create custom form validators in Angular?

• What is ValidatorFn, and how do you use it?

• How do you handle asynchronous validation?

36. Memory Management

• How do you handle memory leaks in Angular?

• How can you prevent memory leaks, particularly with subscriptions in Angular?

Advanced Topics

1. What is Angular Universal?

2. What is Ahead-of-Time (AOT) compilation? What are its benefits over Just-in-Time (JIT)?

3. What is Angular Ivy?

4. What are dynamic components?

5. How does Angular support Internationalization (i18n)?

6. What is a service worker, and how is it implemented in Angular?

7. How does Angular prevent XSS (Cross-Site Scripting) attacks?

8. What are the differences between different Angular versions (AngularJS, Angular 2, etc.)?

9. What are Angular Signals, and how do they work?

10. How does differential loading improve performance?

• What is view encapsulation in Angular?

• What are Angular signals, and how are they used?

Miscellaneous

1. How does Angular Material work?

2. How do you include third-party libraries (e.g., Bootstrap, SASS) into an Angular project?

3. What is the purpose of ng-content and content projection?

4. What are Angular elements and custom elements?

Behavioral & Design Patterns

• What are common design patterns used in Angular applications?

• Explain the Singleton, Observer, and Facade patterns in Angular context.

• How do you structure a scalable Angular application?

Common Pitfalls & Best Practices

• What are some common performance bottlenecks in Angular applications, and how can they be mitigated?

• What are some best practices for optimizing an Angular app for production?

Advanced Use Cases

• How do you integrate WebSocket connections in Angular?

• How can you use Angular with third-party libraries like D3.js or Chart.js?

• What are hybrid AngularJS/Angular applications, and how do you work with them?

Angular Animations

1. What is Angular Animation?

2. How do you create animations using the state, style, and animate functions?

3. How do you trigger animations on route transitions?