💡 Top 100+ Angular Interview Questions and Answers (Basic to Advanced) with Examples

 🧠 Introduction

Angular is one of the most powerful front-end frameworks for building dynamic single-page applications (SPAs).
This article will help you prepare for Angular interviews — whether you’re a beginner or senior developer — with clear explanations, code examples, and version comparisons (from AngularJS to Angular 17).

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🟢 Section 1: Basic Angular Interview Questions

1. What is Angular?

Answer:
Angular is a TypeScript-based front-end framework developed by Google for building dynamic, responsive web applications.

It provides features like:

• Two-way data binding

• Dependency Injection (DI)

• Directives, Components, Services

• Routing and Forms handling

Example:

@Component({
  selector: 'app-hello',
  template: `<h1>Hello Angular!</h1>`
})
export class HelloComponent {}

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2. What are Components in Angular?

Answer:
Components are the building blocks of an Angular app.
They control a part of the UI through a template, logic (TypeScript), and styles (CSS).

Structure:

@Component({
  selector: 'app-user',
  templateUrl: './user.component.html',
  styleUrls: ['./user.component.css']
})
export class UserComponent {
  name = 'Hasitha';
}

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3. What is a Module in Angular?

Answer:
A module (@NgModule) is a container for components, directives, pipes, and services.

Example:

@NgModule({
  declarations: [AppComponent, UserComponent],
  imports: [BrowserModule],
  bootstrap: [AppComponent]
})
export class AppModule {}

---

4. What are Directives?

Answer:
Directives are instructions in the DOM.

• Structural Directives: *ngIf, *ngFor

• Attribute Directives: ngStyle, ngClass

Example:

<p *ngIf="isVisible">This is visible!</p>
<li *ngFor="let item of list">{{ item }}</li>

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5. What is Data Binding?

Answer:
It connects the component logic and template view.

Type	Syntax	Example
Interpolation	{{}}	{{name}}
Property Binding	[property]	<img [src]="imageUrl">
Event Binding	(event)	<button (click)="onClick()">
Two-way Binding	[(ngModel)]	<input [(ngModel)]="username">

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🧩 Section 2: Intermediate Angular Interview Questions

6. What is Dependency Injection (DI)?

Answer:
A design pattern in which a class receives its dependencies from an external source rather than creating them itself.

Example:

@Injectable()
export class UserService {
  getUsers() { return ['Hasitha', 'Cherry']; }
}

@Component({ ... })
export class UserComponent {
  constructor(private userService: UserService) {}
}

---

7. What are Pipes in Angular?

Answer:
Pipes transform data in the template.

Example:

<p>{{ today | date:'fullDate' }}</p>
<p>{{ 1234.56 | currency:'INR' }}</p>

Custom Pipe:

@Pipe({ name: 'capitalize' })
export class CapitalizePipe implements PipeTransform {
  transform(value: string): string {
    return value.toUpperCase();
  }
}

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8. What is Routing in Angular?

Answer:
Routing allows navigation between different views (components).

Example:

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent }
];
@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule {}

---

9. What are Observables in Angular?

Answer:
Observables (from RxJS) are used to handle asynchronous data streams like HTTP requests or user input events.

Example:

this.http.get('https://api.example.com/users')
  .subscribe(data => console.log(data));

---

10. What are Lifecycle Hooks?

Answer:
Hooks allow developers to tap into component life events.

Hook	Description
ngOnInit()	Runs after component initialization
ngOnChanges()	Runs when input properties change
ngOnDestroy()	Runs before component destruction

Example:

ngOnInit() {
  console.log('Component initialized');
}

---

🔥 Section 3: Advanced Angular Interview Questions

11. What is Change Detection in Angular?

Answer:
Angular automatically checks and updates the DOM when data changes.
You can control this using ChangeDetectionStrategy.OnPush for performance.

@Component({
  selector: 'app-demo',
  template: `{{user.name}}`,
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class DemoComponent { }

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12. What are Guards in Angular Routing?

Answer:
Guards control access to routes (like authentication).

Example:

@Injectable()
export class AuthGuard implements CanActivate {
  canActivate(): boolean {
    return !!localStorage.getItem('token');
  }
}

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13. What is Lazy Loading?

Answer:
Lazy loading loads feature modules on demand to reduce initial load time.

Example:

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

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14. What is Ahead-of-Time (AOT) Compilation?

Answer:
AOT compiles Angular templates at build time (not runtime), making apps faster.

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15. What are Standalone Components (Angular 15+)?

Answer:
Angular 15 introduced standalone components that don’t require NgModule.

Example:

@Component({
  standalone: true,
  selector: 'app-hello',
  template: `<h1>Hello Standalone!</h1>`,
  imports: [CommonModule]
})
export class HelloComponent {}

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🧱 Section 4: Important TypeScript Topics for Angular

TypeScript Feature	Description	Example
Interfaces	Defines structure of objects	interface User { name: string; age: number; }
Generics	Reusable type-safe code	function identity<T>(arg: T): T { return arg; }
Decorators	Add metadata to classes	@Component({...})
Enums	Define constants	enum Color { Red, Green, Blue }
Access Modifiers	Control visibility	private, public, protected
Async/Await	Simplify Promises	await this.http.get()

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⚖️ Section 5: Major Differences Between Angular Versions

Feature	AngularJS (1.x)	Angular 2–8	Angular 9–13	Angular 14–17
Language	JavaScript	TypeScript	TypeScript	TypeScript
Architecture	MVC	Component-based	Ivy Compiler	Standalone Components
Mobile Support	No	Yes	Yes	Yes
Compilation	Runtime (JIT)	AOT supported	Ivy Renderer	Next-gen compiler
Forms	ng-model	Reactive & Template-driven	Improved forms API	Typed Forms
Routing	$routeProvider	RouterModule	Lazy Loading	Enhanced standalone routing
Build Tool	Grunt/Gulp	Angular CLI	Angular CLI	Vite integration (Angular 17)

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🧰 Section 6: Common Angular Coding Questions

Example 1: Two-Way Data Binding

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

Example 2: Using HTTPClient

this.http.get('https://api.example.com/posts')
  .subscribe(posts => this.posts = posts);

Example 3: Parent to Child Communication

// parent.component.html
<app-child [data]="userData"></app-child>

// child.component.ts
@Input() data: any;

Example 4: Custom Directive

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

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🎯 Final Tips for Angular Interviews

✅ Revise core concepts: Components, Services, Observables, DI
✅ Write small sample projects using Angular CLI
✅ Understand TypeScript fundamentals
✅ Learn performance techniques (Lazy Loading, OnPush, AOT)
✅ Know version updates from Angular 2 → 17

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