51 Angular interview Questions and Answers PDF 2025

Angular is a popular front end web framework developed by Google. It helps developers build fast, dynamic, and modern websites and web applications. Many companies use Angular to create single page applications, where the web page updates smoothly without reloading every time. This makes it a valuable skill in web development jobs.

Angular works using HTML, CSS, and TypeScript (a special version of JavaScript). Developers use Angular to create user interfaces, handle data, connect APIs, and manage application logic all within one framework. Knowing Angular also means understanding components, services, routing, forms, and dependency injection.

If you want a job as an Angular Developer, preparing for the interview is very important. Interviews often test your practical skills, problem solving abilities, and understanding of Angular’s features and real world uses. Good preparation helps you answer confidently, handle scenario-based questions, and showcase your skills.

Here, we are sharing Top Angular interview questions and answers. This guide covers technical topics, real life scenarios, and top asked questions. We are also providing PDF download, so you can prepare offline easily anytime.

Basic Angular Interview Questions and Answers for Freshers

Let’s start with fundamental Angular interview questions suitable for entry-level or junior positions. As we progress, the questions will become more challenging. Sample answers will be provided, but it is important that you formulate your own responses in your own words.

Que 1. What is a Component in Angular?

Answer:
A Component is the basic building block of an Angular application. It controls a part of the user interface using its template, CSS, and logic written in TypeScript. Each component is a class decorated with @Component().

Que 2. What is the purpose of NgModule in Angular?

Answer:
NgModule is a decorator that helps organize related components, directives, services, and pipes into a cohesive block. The @NgModule() decorator defines the module’s metadata, like declarations, imports, and providers.

Que 3. What is Data Binding in Angular?

Answer:
Data Binding connects the UI and the component logic. Angular supports four types of data binding:

• Interpolation ({{ }})
• Property Binding ([property])
• Event Binding ((event))
• Two-Way Binding ([(ngModel)])

Que 4. What is Two-Way Data Binding?

Answer:
Two-Way Data Binding allows automatic synchronization of data between the UI and the component class. It uses the [(ngModel)] directive to bind both ways.

Example:

<input [(ngModel)]="userName">
<p>{{userName}}</p>

Que 5. What is a Directive in Angular?

Answer:
A Directive is a special instruction in Angular that modifies the behavior or appearance of DOM elements.
Types:

• Structural Directives (like *ngIf, *ngFor)
• Attribute Directives (like [ngClass], [ngStyle])

Que 6. Explain the use of *ngFor directive.

Answer:
*ngFor is a Structural Directive used to loop over a list of items and create a template for each item.

Example:

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

Que 7. What is Dependency Injection in Angular?

Answer:
Dependency Injection (DI) is a design pattern where services or objects are provided to components, making them easier to manage and test. Angular uses DI to inject services into constructors automatically.

Que 8. What is a Service in Angular?

Answer:
A Service is a class used to share data or business logic across multiple components. It’s commonly used with Dependency Injection to fetch data from APIs or perform reusable tasks.

Example:

@Injectable({
  providedIn: 'root'
})
export class DataService { }

Que 9. What is Routing in Angular?

Answer:
Routing in Angular allows navigation between different pages or views within the application without reloading the entire page. It uses the Angular Router module to map URL paths to components.

Que 10. How do you create a new Angular Component?

Answer:
Use Angular CLI command:

ng generate component component-name

This creates a component with .ts, .html, .css, and .spec.ts files automatically.

Que 11. What is Lifecycle Hook in Angular?

Answer:
Lifecycle Hooks are special methods that allow developers to tap into key moments of a component’s life, such as initialization, changes, or destruction. Common hooks include:

• ngOnInit()
• ngOnChanges()
• ngOnDestroy()

Que 12. What is ngOnInit()?

Answer:
ngOnInit() is a lifecycle hook method automatically called by Angular after the component’s constructor. It’s used to initialize component data or perform startup logic.

Que 13. What are Observables in Angular?

Answer:
Observables are used for handling asynchronous data streams, such as HTTP requests or event handling. Angular commonly uses Observables from RxJS for reactive programming.

Example:

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

Que 14. What is HttpClientModule?

Answer:
HttpClientModule is a module in Angular used for making HTTP requests to servers or APIs. It must be imported in the app module to use the HttpClient service.

Example:

import { HttpClientModule } from '@angular/common/http';

Que 15. What is Lazy Loading in Angular?

Answer:
Lazy Loading is a technique where certain modules are loaded only when needed, reducing the initial loading time of the application and improving performance.

Que 16. What is AOT Compilation?

Answer:
AOT (Ahead-of-Time) Compilation compiles Angular HTML and TypeScript code into efficient JavaScript code before the browser downloads and runs it. This improves performance and reduces page load time.

Que 17. What are Pipes in Angular?

Answer:
Pipes are used to transform data before displaying it in the UI. Angular provides built-in pipes like date, uppercase, currency, and also allows creating custom pipes.

Example:

<p>{{ birthday | date }}</p>

Que 18. What is the difference between Template-Driven Forms and Reactive Forms?

Answer:

Feature	Template-Driven Forms	Reactive Forms
Form Creation	In HTML Template	In Component Class
Suitable For	Simple Forms	Complex Forms
Form Control	Less Flexible	Highly Scalable
Validation	Directive-Based	Code-Based

Que 19. How can you handle errors in Angular HTTP calls?

Answer:
Use catchError() operator from RxJS to handle errors gracefully when making HTTP requests.

Example:

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

Que 20. What is the Angular CLI and why is it useful?

Answer:
Angular CLI (Command Line Interface) is a tool that helps automate common development tasks like creating components, services, and modules, building projects, and running unit tests. It simplifies Angular project setup and management.

Also Check: Technical Interview Questions and Answers

Advanced Angular Interview Questions and Answers for Experienced

Que 21. What is Change Detection in Angular?

Answer:
Change Detection is the process Angular uses to check if component data has changed and automatically updates the DOM to reflect those changes. It triggers after events like user actions, HTTP responses, or timers.

Que 22. Explain Default vs OnPush Change Detection strategies.

Answer:

• Default Strategy: Angular checks the entire component tree for changes.
• OnPush Strategy: Angular checks for changes only when the component’s input properties change or when triggered manually, improving performance in large applications.

Que 23. What is the async pipe and its benefits?

Answer:
The async pipe is used in templates to automatically subscribe to Observables or Promises. It handles subscription and unsubscription automatically, reducing the risk of memory leaks and making code cleaner.

Que 24. What is a Resolver in Angular Routing?

Answer:
A Resolver is used to fetch data before a route is activated. This ensures the required data is available when the component loads. Resolvers are defined as services and added to route configurations.

Que 25. How do you implement lazy loading for modules in Angular?

Answer:
Use the Angular Router to configure lazy loading by loading feature modules dynamically with the loadChildren property in route configurations.

Example:

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

Que 26. What are Guards in Angular?

Answer:
Guards are interfaces that determine whether a route can be activated, deactivated, or loaded. Types include:

• CanActivate
• CanActivateChild
• CanDeactivate
• CanLoad

They help in securing routes and controlling navigation flow.

Que 27. Explain Dependency Injection Hierarchy in Angular.

Answer:
Angular uses a hierarchical injector system:

• Root Injector: Shared across the entire app.
• Module Injector: Specific to a module.
• Component Injector: Local to the component and its children.
  This system controls service scopes and memory management.

Que 28. What is the role of interceptors in Angular?

Answer:
Interceptors are used to modify HTTP requests or responses globally. Common uses include:

• Adding authorization tokens to headers
• Logging requests
• Handling global errors

Example:

@Injectable()
export class AuthInterceptor implements HttpInterceptor { }

Que 29. What is Dynamic Component Loading?

Answer:
Dynamic Component Loading allows developers to create and inject components at runtime instead of declaring them statically in templates. This is done using ViewContainerRef and ComponentFactoryResolver.

Que 30. How do you handle memory leaks in Angular?

Answer:

• Use async pipe where possible to auto-manage subscriptions
• Manually unsubscribe in ngOnDestroy() using Subscription.unsubscribe()
• Use takeUntil() pattern in Observables
• Avoid excessive DOM manipulations

Que 31. What is Zone.js and its role in Angular?

Answer:
Zone.js is a library used by Angular to track and manage asynchronous operations. It helps Angular know when to run Change Detection automatically after tasks like HTTP calls or timers complete.

Que 32. Explain Angular Universal.

Answer:
Angular Universal is a technology that enables Server-Side Rendering (SSR) of Angular applications. It improves SEO, reduces first-page load time, and enhances user experience on slower networks.

Que 33. How can you optimize Angular application performance?

Answer:

• Use OnPush change detection
• Implement lazy loading
• Minify and compress files
• Use trackBy with *ngFor
• Use Pure Pipes and avoid unnecessary subscriptions
• Preload critical resources

Que 34. What is the difference between Pure and Impure Pipes?

Answer:

• Pure Pipes: Called only when input data changes, improving performance.
• Impure Pipes: Called on every change detection cycle, which may reduce performance.

Example:

@Pipe({ name: 'myPipe', pure: false })

Que 35. How do you share data between unrelated components?

Answer:

• Use a shared service with a Subject or BehaviorSubject
• Use Angular’s Dependency Injection to inject the shared service
• Components can subscribe to the Subject to receive updates

Que 36. What is the Renderer2 service?

Answer:
Renderer2 is used to safely manipulate DOM elements in Angular. It’s useful for platform independence and prevents direct access to the DOM, enhancing security and testing.

Example:

this.renderer.setStyle(element, 'color', 'blue');

Que 37. How does Angular handle forms validation?

Answer:
Angular provides:

• Template-Driven Validation: Using built-in directives like required, minlength.
• Reactive Form Validation: Using Validators in FormBuilder.

Both approaches support custom validators for advanced needs.

Que 38. What is State Management in Angular?

Answer:
State management involves handling shared application data consistently. Tools like NgRx or Akita are used to manage state using RxJS, reducers, actions, and stores to avoid complex data flows.

Que 39. What is Tree Shaking in Angular?

Answer:
Tree Shaking is a build optimization process where unused code is removed during the build phase, resulting in smaller, faster applications. Angular CLI uses Webpack to perform tree shaking.

Que 40. Explain Ivy Renderer.

Answer:
Ivy is Angular’s next-generation rendering engine that improves build speed, debugging, and runtime performance. It enables smaller bundle sizes and allows lazy loading of individual components. Ivy is enabled by default in Angular versions 9 and above.

Scenario Based Angular Interview Questions and Answers

Que 41. A component is not updating its view even after changing a variable. What could be the issue?

Answer:
The component might be using OnPush change detection strategy. In this case, the view only updates when input properties change or when markForCheck() is manually triggered using ChangeDetectorRef.

Que 42. How would you handle API errors globally in an Angular app?

Answer:
Use HTTP Interceptors to catch all HTTP errors at a global level. Inside the interceptor’s catchError() block, handle errors like unauthorized access or server failures and display appropriate messages using a service or notification component.

Que 43. You need to preload data before showing a route page. What approach will you use?

Answer:
Implement a Resolver service that fetches necessary data before the route is activated. Add this resolver in the route configuration so the component loads only after the data is ready.

Que 44. Your app is loading slowly. How will you optimize performance?

Answer:

• Use Lazy Loading for feature modules
• Implement OnPush change detection
• Use trackBy in *ngFor loops
• Load images with lazy loading
• Remove unused code via tree shaking
• Minify and compress files using production build

Que 45. A user logs in successfully but the dashboard shows old data. How do you fix this?

Answer:
Avoid caching sensitive API calls by adding cache-control headers. Also, clear local storage or session storage during logout and refresh the required services or Observables after login to fetch fresh data.

Que 46. Your component makes multiple API calls on every change detection. What is wrong?

Answer:
API calls should not be placed directly inside templates or in functions that run during every change detection. Use lifecycle hooks like ngOnInit() to call APIs once or manage subscriptions properly to avoid repeated HTTP requests.

Que 47. You’re required to pass data from a child component to its parent. How will you do it?

Answer:
Use the @Output() decorator and EventEmitter in the child component to emit events. The parent component listens to these events using event binding to receive the data.

Example:

@Output() dataEvent = new EventEmitter<string>();
this.dataEvent.emit('sample data');

Que 48. You need to display different menus for different users after login. What approach will you follow?

Answer:
Store user roles or permissions in a shared service after login. Based on the role, conditionally render different menus using *ngIf in the template. This logic should be managed centrally via service for consistency across components.

Que 49. Your form validations are complex and need custom rules. What solution will you apply?

Answer:
Use Reactive Forms with custom validators. Define validator functions that check complex conditions and attach them to form controls using setValidators() during form building.

Que 50. How will you handle memory leaks in a component that subscribes to Observables?

Answer:

• Unsubscribe manually using Subscription.unsubscribe() in the ngOnDestroy() lifecycle hook
• Use the takeUntil() pattern with a Subject to manage unsubscriptions automatically
• Prefer using the async pipe, which handles unsubscription automatically in templates

Que 51. Your team wants a feature that loads modules only after a user logs in. What approach do you suggest?

Answer:
Use Lazy Loading with Route Guards (CanLoad). Protect routes by checking authentication inside the guard before loading the feature module. This ensures that modules load only when necessary.

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FAQ: Angular Interview Questions

Conclusion

We have shared basic, advanced, and scenario-based questions above, suitable for entry level or junior roles as well as experienced or senior positions. Now, you can prepare your own answers with the help of this guide. We have also provided a PDF to make it easier for you to access these questions anytime.