💡 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).

---

🟢 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 {}

---

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';
}

---

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>

---

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">

---

🧩 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();
  }
}

---

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 { }

---

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');
  }
}

---

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) }
];

---

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

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

---

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 {}

---

🧱 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()

---

⚖️ 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)

---

🧰 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';
  }
}

---

🎯 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

Angular interview questions, Angular 17 questions, Angular advanced interview, Angular TypeScript topics, Angular code examples, Angular version comparison, Angular developer interview, Angular coding round

Angular Core Concepts Explained: Components, Modules, Templates, Directives, and Pipes (with Examples)

 If you’re learning Angular or preparing for an Angular interview, understanding the building blocks of Angular applications is crucial. In this article, we’ll explore Components, Modules, Templates, Directives, and Pipes with clear explanations, practical examples, and SEO-friendly insights that will help you in both real-world development and blogging.

✅ Keywords to target: Angular Components, Angular Modules, Angular Templates, Angular Directives, Angular Pipes, Angular basics, Angular interview questions, Angular tutorial.

---

1. Angular Components

Definition:
A Component in Angular is the smallest UI building block. Each component controls a part of the view (HTML + CSS + logic).

Key Features of Components:

• Built with a TypeScript class

• Connected to an HTML template

• Scoped styles and encapsulation

• Communicate using @Input() and @Output()

Example: Todo Item Component

import { Component, Input, Output, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-todo-item',
  template: `
    <div (click)="toggle()" [class.done]="todo.done">
      {{ todo.title }}
      <button (click)="remove($event)">Remove</button>
    </div>
  `,
  styles: [`.done { text-decoration: line-through; }`]
})
export class TodoItemComponent {
  @Input() todo!: { id: number; title: string; done: boolean };
  @Output() removed = new EventEmitter<number>();
  @Output() toggled = new EventEmitter<number>();

  toggle() { this.toggled.emit(this.todo.id); }
  remove(e: Event) { e.stopPropagation(); this.removed.emit(this.todo.id); }
}

👉 SEO Tip: Use headings like “What is Angular Component?” and “Angular Component Example” — they match common search queries.

---

2. Angular Modules

Definition:
An NgModule groups related Components, Directives, and Pipes together. Every Angular app starts with a root module (AppModule), and you can create feature modules for large applications.

Example: AppModule

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent } from './app.component';
import { TodoItemComponent } from './todo-item.component';

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

👉 SEO Keyword Phrase: Angular Modules example, feature module in Angular, AppModule in Angular

---

3. Angular Templates

Definition:
A Template in Angular is HTML with Angular syntax (bindings, directives, and pipes). Templates define how data is displayed in the UI.

Example Template Features

<h1>{{ title }}</h1>                     <!-- Interpolation -->
<img [src]="avatarUrl" />                <!-- Property binding -->
<button (click)="onSave()">Save</button> <!-- Event binding -->
<input [(ngModel)]="name" />             <!-- Two-way binding -->
<ul>
  <li *ngFor="let item of items">{{ item | uppercase }}</li>
</ul>

👉 SEO Keywords: Angular template syntax, Angular interpolation, Angular ngFor, Angular ngIf.

---

4. Angular Directives

Definition:
A Directive is used to extend HTML behavior.

• Structural Directives: Change DOM structure (*ngIf, *ngFor).

• Attribute Directives: Change appearance/behavior of an element (ngStyle, ngClass, or custom directives).

Custom Attribute Directive Example: Highlight

import { Directive, HostBinding, HostListener, Input } from '@angular/core';

@Directive({ selector: '[appHighlight]' })
export class HighlightDirective {
  @Input('appHighlight') color = 'yellow';
  @HostBinding('style.backgroundColor') bg?: string;

  @HostListener('mouseenter') onEnter() { this.bg = this.color; }
  @HostListener('mouseleave') onLeave() { this.bg = ''; }
}

Usage:

<p appHighlight="lightblue">Hover to Highlight</p>

👉 SEO Keywords: Angular directives, Angular structural directives, Angular attribute directives, custom directive in Angular.

---

5. Angular Pipes

Definition:
A Pipe transforms data in templates without changing the actual object. Angular provides built-in pipes (date, currency, async) and you can create custom pipes.

Custom Pipe Example: Truncate

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({ name: 'truncate' })
export class TruncatePipe implements PipeTransform {
  transform(value: string, limit = 20): string {
    return value.length > limit ? value.slice(0, limit) + '…' : value;
  }
}

Usage:

<p>{{ longText | truncate:30 }}</p>

👉 SEO Keywords: Angular pipes, Angular custom pipe, Angular date pipe, Angular async pipe.

---

✅ Conclusion

• Components → UI building blocks

• Modules → Grouping and organization

• Templates → Define structure and binding

• Directives → Add behavior or structure to DOM

• Pipes → Transform data in views

By mastering these five concepts, you’ll have a solid foundation in Angular development. Whether you’re preparing for Angular interview questions or building enterprise-grade applications, understanding these basics is essential.