Top 40 Angular Coding Interview Questions and Answers

Did you know that according to a 2019 StackOverflow survey, 30.7% of software engineers use both AngularJS and the newer Angular 2+ versions? This shows just how widely adopted Angular has become in building scalable, high-performance applications. The demand for Angular developers is closely tied to the number of companies relying on this framework for their tech stacks. In this blog, Angular coding interview questions and answers, we’ll walk you through essential coding questions to help you prepare for your next Angular interview with confidence.

Angular Coding Interview Questions and Answers For Entry-Level Candidates

For entry-level Angular roles, interviewers typically focus on understanding candidates’ grasp of the basics, such as components, templates, and data binding. These foundational concepts show a solid start to Angular development skills. Now, let us look at a few Angular coding questions and answers specific to fresher Angular candidates.

Q1. How do you create a new Angular component using the CLI?

Sample Answer: Creating a new Angular component is straightforward with Angular’s Command Line Interface (CLI). The CLI generates the necessary files and updates the module automatically. This ensures that your new component is ready for use immediately after creation.

ng generate component componentName

Q2. How do you create and use a simple Angular service to get a greeting message?

Sample Answer: In Angular, services are essential for sharing data and functionality across components. Below is a simple example of how to create and use a service to get a greeting message.

// greeting.service.ts
import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root',
})
export class GreetingService {
  getGreeting(): string {
    return 'Hello, welcome to Angular!';
  }
}

// app.component.ts
import { Component } from '@angular/core';
import { GreetingService } from './greeting.service';

@Component({
  selector: 'app-root',
  template: `<h1>{{ greeting }}</h1>`,
})
export class AppComponent {
  greeting: string;

  constructor(private greetingService: GreetingService) {
    this.greeting = this.greetingService.getGreeting();
  }
}

Q3. Write a code example for two-way data binding in Angular.

Sample Answer: Two-way data binding allows you to synchronize data between the model and the view. This is commonly achieved using the ngModel directive, which updates the model when the user modifies the input field and vice versa.

<input [(ngModel)]="name" />

Q4. How would you set up basic routing between two components in Angular?

Sample Answer: Setting up routing is essential for navigating between different components in an Angular application. By defining routes in the routing module, you can specify which component should be displayed for a given path. This enhances user experience by allowing seamless navigation.

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent },
];

Q5. Show how to pass data from a parent component to a child component using @Input.

Sample Answer: To share data from a parent to a child component in Angular, you use the @Input decorator. This allows the parent to bind properties directly to the child, enabling dynamic data passing. It’s a powerful way to maintain a clean component architecture.

@Input() childData: string;

Q6. How can you emit an event from a child component to a parent component using @Output?

Sample Answer: The @Output decorator in Angular allows child components to send events or data back to their parent components. This is typically done through an EventEmitter, which notifies the parent about changes or actions taken in the child.

@Output() childEvent = new EventEmitter<string>();

Q7. Write an example to display a list of items using *ngFor.

Sample Answer: The *ngFor directive is used to iterate over a collection and render a list of elements dynamically. This is particularly useful for displaying arrays of data, such as user lists or product catalogs, in an organized manner.

<ul><li *ngFor="let item of items">{{ item }}</li></ul>

Q8. How do you conditionally display content using *ngIf?

Sample Answer: Using the *ngIf directive allows you to conditionally render elements based on boolean expressions. This is useful for controlling the visibility of elements based on user interactions or application state.

<div *ngIf="isVisible">Content is visible</div>

Q9. How do you handle form input using Angular’s reactive forms?

Sample Answer: Reactive forms in Angular provide a model-driven approach to handling form inputs. This involves creating a FormGroup and FormControl instances, allowing for better validation and dynamic form handling. This method is ideal for complex forms requiring high customizability.

form = new FormGroup({ name: new FormControl('') });

Q10. Show how to fetch data from an API using Angular’s HttpClient.

Sample Answer: To retrieve data from external APIs in Angular, you can use the HttpClient service. This service provides a straightforward API for making HTTP requests and handling responses, making it easier to interact with backend services.

this.http.get('api/data').subscribe(data => console.log(data));

Q11. Write a code example to use ngClass to add conditional classes.

Sample Answer: The ngClass directive dynamically assigns CSS classes based on conditions. This allows for flexible styling based on component states, enhancing the visual feedback for users when interacting with the application.

<div [ngClass]="{ 'active': isActive }">Toggle Class</div>

Q12. How can you configure lazy loading for a feature module in Angular?

Sample Answer: Lazy loading is a technique that improves application performance by loading feature modules on demand rather than at startup. This helps reduce the initial load time of the application, making it faster for users.

{ path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }

Q13. How do you define a custom directive in Angular?

Sample Answer: Custom directives extend the behavior of existing elements in Angular applications. You can create a directive to encapsulate specific functionality and apply it to any element in your templates, promoting reusability and clean code.

@Directive({ selector: '[appHighlight]' })
export class HighlightDirective { 
  constructor(el: ElementRef) { 
    el.nativeElement.style.backgroundColor = 'yellow'; 
  } 
}

Pro Tip: To excel in your Angular coding interview, focus on mastering the TCS Angular interview questions and answers. Additionally, enhance your understanding by taking an Angular course that emphasizes practical coding challenges. This combination will prepare you to tackle questions confidently and demonstrate your expertise effectively.

Angular Coding Interview Questions and Answers For Mid-Level Candidates

At the mid-level, Angular questions cover more complex aspects like lifecycle hooks, services, and dependency injection. Interviewers want to see how well candidates manage these elements for functional, maintainable applications. Now, let us look at a few Angular coding questions and answers designed for mid-level Angular candidates.

Q14. What is the purpose of Angular interceptors, and how can you create one?

Sample Answer: Angular interceptors are used to modify HTTP requests and responses. They can handle tasks like adding headers, logging requests, and managing authentication. By implementing the HttpInterceptor interface, you can create a custom interceptor that integrates seamlessly into your HTTP workflow.

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler) {
    const cloned = req.clone({ headers: req.headers.set('Authorization', 'Bearer token') });
    return next.handle(cloned);
  }
}

Q15. How can you create a custom pipe in Angular?

Sample Answer: Custom pipes allow you to transform data within templates. By implementing the PipeTransform interface, you can create a pipe that encapsulates specific transformation logic, which enhances the readability and maintainability of your code.

@Pipe({ name: 'exponentialStrength' })
export class ExponentialStrengthPipe implements PipeTransform {
  transform(value: number, exponent: string): number {
    const exp = parseFloat(exponent);
    return Math.pow(value, isNaN(exp) ? 1 : exp);
  }
}

Q16. How do you implement dependency injection in Angular services?

Sample Answer: Dependency injection (DI) in Angular allows you to manage service instances efficiently. By declaring dependencies in the constructor of a component or service, Angular’s injector provides the necessary instances, promoting modularity and reusability.

@Injectable({ providedIn: 'root' })
export class UserService {
  constructor(private http: HttpClient) {}
}

Q17. How can you handle asynchronous operations in Angular using Observables?

Sample Answer: Observables are a key part of Angular’s reactive programming model. They allow you to work with asynchronous data streams, making it easier to manage events, HTTP requests, and other time-based operations.

this.http.get<User[]>('api/users').subscribe(users => console.log(users));

Q18. Explain how to set up and use Angular guards for route protection.

Sample Answer: Angular guards help you control access to routes based on specific conditions, such as authentication. By implementing CanActivate or CanDeactivate interfaces, you can create guards that determine if a user can access a certain route.

@Injectable({ providedIn: 'root' })
export class AuthGuard implements CanActivate {
  canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): boolean {
    return this.authService.isLoggedIn();
  }
}

Q19. How do you create a reactive form with form validation in Angular?

Sample Answer: Reactive forms provide a robust approach to managing forms in Angular. By creating a FormGroup and defining validation rules, you can ensure that user input is validated effectively before processing it.

this.form = new FormGroup({
  name: new FormControl('', [Validators.required, Validators.minLength(4)]),
});

Q20. Explain how to implement lazy loading for a feature module.

Sample Answer: Lazy loading improves performance by loading feature modules only when needed. By using the loadChildren property in the route configuration, you can define which module to load on specific routes, reducing the initial load time.

const routes: Routes = [
  { path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) },
];

Q21. What are the differences between a service and a factory in Angular?

Sample Answer: Both services and factories are used for dependency injection, but they differ in how they are instantiated. A service is instantiated by Angular and is a singleton, while a factory can return a new instance every time it is called, giving you more control over instance creation.

Code Example:

Service:

app.service('MyService', function() {
  this.sayHello = function() {
    return 'Hello from Service!';
  };
});

Factory:

app.factory('MyFactory', function() {
  return {
    sayHello: function() {
      return 'Hello from Factory!';
    }
  };
});

Q22. How do you use ngIf with an else clause in Angular?

Sample Answer: The ngIf directive in Angular can be extended with an else clause to conditionally display alternate content. This feature enhances template readability and allows for cleaner conditional rendering without extra markup.

<div *ngIf="isLoggedIn; else loginTemplate">Welcome!</div>
<ng-template #loginTemplate><p>Please log in</p></ng-template>

Q23. How can you make HTTP requests with error handling in Angular?

Sample Answer: Handling errors in HTTP requests is crucial for a good user experience. By using the catchError operator in your observables, you can gracefully handle errors and provide feedback to the user or log the errors.

this.http.get('api/data').pipe(catchError(error => {
  console.error('Error occurred:', error);
  return throwError(error);
})).subscribe();

Q24. How can you implement a custom directive that changes the background color of an element?

Sample Answer: Custom directives can modify the behavior or appearance of elements in Angular. By creating a directive that utilizes ElementRef and Renderer2, you can easily alter styles based on specific conditions or user interactions.

@Directive({ selector: '[appBackgroundColor]' })
export class BackgroundColorDirective {
  constructor(el: ElementRef, renderer: Renderer2) {
    renderer.setStyle(el.nativeElement, 'backgroundColor', 'yellow');
  }
}

Q25. How do you implement state management in Angular using NgRx?

Sample Answer: NgRx provides a powerful solution for managing state in Angular applications. By creating actions, reducers, and effects, you can centralize and manage application state effectively, improving maintainability and scalability.

export const addItem = createAction('[Items] Add Item', props<{ item: Item }>());

Q26. How can you create a service that handles caching in Angular?

Sample Answer: Caching responses can significantly improve performance by reducing redundant network requests. By creating a service that stores and retrieves cached data, you can enhance the user experience by providing instant data access without repeated API calls.

@Injectable({ providedIn: 'root' })
export class CacheService {
  private cache = new Map<string, any>();
  
  get(key: string) {
    return this.cache.get(key);
  }

  set(key: string, value: any) {
    this.cache.set(key, value);
  }
}

Angular Coding Interview Questions and Answers For Experienced-Level Candidates

For expert roles, questions often delve into advanced areas such as state management, performance tuning, and custom directives. This level gauges a candidate’s ability to optimize and scale applications for demanding Angular projects. Now, let us look at a few Angular coding interview questions for experienced-level candidates.

Q27. How can you implement server-side rendering (SSR) in Angular?

Sample Answer: Server-side rendering improves performance and SEO by rendering the application on the server. Angular Universal is used for this purpose, allowing you to serve the initial HTML from the server, resulting in a faster first page load and better indexing by search engines.

ng add @nguniversal/express-engine

Q28. Explain how to optimize performance in Angular applications using ChangeDetectionStrategy.

Sample Answer: Using ChangeDetectionStrategy.OnPush can significantly improve performance by reducing the number of checks Angular performs. This strategy instructs Angular to only check the component when its input properties change or an event occurs, minimizing unnecessary updates.

@Component({
  selector: 'app-my-component',
  changeDetection: ChangeDetectionStrategy.OnPush,
  templateUrl: './my-component.component.html'
})
export class MyComponent { /* Component logic */ }

Q29. What is the role of Zone.js in Angular applications?

Sample Answer: Zone.js is a library that creates an execution context to detect changes in an Angular application. It allows Angular to be aware of asynchronous operations, enabling automatic change detection and ensuring that the UI stays in sync with the data model.

Zone.current.fork({ name: 'myZone' }).run(() => { /* Asynchronous code */ });

Q30. How do you implement dynamic component loading in Angular?

Sample Answer: Dynamic component loading enables you to load components at runtime based on specific conditions. By using ComponentFactoryResolver, you can create and insert components into the view dynamically, enhancing the flexibility of your application.

const componentFactory = this.componentFactoryResolver.resolveComponentFactory(MyComponent);
this.containerRef.clear();
this.containerRef.createComponent(componentFactory);

Q31. Explain how to create a custom form control using ControlValueAccessor.

Sample Answer: To create a custom form control, you need to implement the ControlValueAccessor interface. This allows Angular to communicate with the control, enabling data binding and validation.

export class MyCustomInputComponent implements ControlValueAccessor {
  writeValue(value: any): void { /* Write value logic */ }
  registerOnChange(fn: any): void { this.onChange = fn; }
}

Q32. How can you implement error handling globally in Angular applications?

Sample Answer: In Angular, you can set up global error handling by creating a custom error handler and configuring it in the AppModule. By providing the custom error handler, Angular will use it across the application to capture and handle unhandled errors.

Here’s how to configure the AppModule to use your global error handler:

import { ErrorHandler } from '@angular/core';
import { GlobalErrorHandler } from './global-error.handler';

@NgModule({
  // Other properties like declarations, imports
  providers: [
    {
      provide: ErrorHandler,
      useClass: GlobalErrorHandler
    },
  ],
  // bootstrap, etc.
})
export class AppModule { }

Q33. How do you manage state in an Angular application using Akita?

Sample Answer: Akita is a state management pattern and library that provides a simple API for managing state in Angular applications. It offers a store, queries, and a powerful state management solution for complex applications.

@Injectable({ providedIn: 'root' })
export class MyStore extends Store<MyState> {
  constructor() { super(initialState); }
}

Q34. What are Angular decorators, and how do you use them effectively?

Sample Answer: Decorators are special functions in Angular that add metadata to classes, properties, methods, or parameters. They allow Angular to understand how to instantiate and configure components, services, and modules.

@Component({ selector: 'app-root', templateUrl: './app.component.html' })
export class AppComponent { /* Component logic */ }

Q35. Explain the purpose of ngrx/store and how it can be implemented.

Sample Answer: ngrx/store provides a reactive state management solution based on the Redux pattern. It helps manage application state in a predictable way, making state changes easier to understand and debug.

export const reducer = createReducer(initialState, on(action, state => ({ ...state, property: value })));

Q36. How do you handle internationalization (i18n) in Angular?

Sample Answer: Angular provides built-in support for internationalization (i18n) through a set of tools and libraries. By marking translatable strings with the i18n attribute and using Angular’s i18n tooling, you can easily adapt your application for different languages.

<p i18n="@@welcomeMessage">Welcome to our application!</p>

Q37. Explain how to implement lazy loading with route parameters in Angular.

Sample Answer: Lazy loading can be combined with route parameters to load modules only when specific routes are accessed. This helps to optimize the initial load time while still allowing dynamic routing based on parameters.

const routes: Routes = [
  { path: 'user/:id', loadChildren: () => import('./user/user.module').then(m => m.UserModule) },
];

Q38. How can you create a multi-step form in Angular?

Sample Answer: Multi-step forms can be implemented using Angular’s reactive forms and component interaction. By managing form state and validation across multiple components, you can create a seamless user experience.

this.form = this.fb.group({
  step1: this.fb.group({ name: ['', Validators.required] }),
  step2: this.fb.group({ address: ['', Validators.required] }),
});

Q39. What strategies can you use for optimizing bundle size in Angular applications?

Sample Answer: Optimizing bundle size can be achieved through techniques like lazy loading, tree shaking, AOT (Ahead-of-Time) compilation, and minimizing third-party dependencies. These strategies enhance application performance and reduce load times.

ng build --prod --optimization

Q40. Explain how to use the Angular CLI for managing environments.

Sample Answer: The Angular CLI provides a way to manage multiple environments by using the file replacements option in angular.json. This allows you to specify different configuration files for different builds, such as development and production.

"fileReplacements": [
  {
    "replace": "src/environments/environment.ts",
    "with": "src/environments/environment.prod.ts"
  }
]

Conclusion

As you prepare for your Angular interview, remember that mastering Angular coding interview questions and answers is crucial for standing out among candidates. Familiarizing yourself with these common questions not only boosts your confidence but also effectively showcases your skills. By focusing on your knowledge of Angular, you can position yourself for success in your job search. To further enhance your understanding of the Angular career landscape, check out our blog on Angular developer salary in India, especially if you’re looking for opportunities at the highest-paying IT companies in India.