Angular remains one of the most popular frontend frameworks for building enterprise-grade web applications. Whether you're a fresher preparing for your first Angular interview or an experienced developer aiming for a senior position, mastering Angular fundamentals and advanced concepts is essential.
In this article, we'll explore the top 100 Angular interview questions that are frequently asked in technical interviews. These questions cover Angular fundamentals, components, directives, services, RxJS, routing, forms, performance optimization, and the latest Angular features such as Signals and Standalone Components.
Angular Basics
1. What is Angular?
Angular is a TypeScript-based open-source web application framework developed by Google. It is used for building dynamic, single-page applications (SPAs).
2. What are the key features of Angular?
Some major features include:
Component-based architecture
Dependency Injection
Two-way data binding
Routing
Reactive programming with RxJS
Built-in form handling
Lazy loading
Server-side rendering
3. What is the difference between AngularJS and Angular?
| AngularJS | Angular |
|---|---|
| JavaScript-based | TypeScript-based |
| MVC architecture | Component-based architecture |
| Uses controllers | Uses components |
| Slower performance | Better performance |
| Limited mobile support | Mobile-friendly |
4. What is a Component?
A component is the fundamental building block of an Angular application. It controls a portion of the user interface.
5. What is a Module in Angular?
Modules help organize related components, directives, pipes, and services into cohesive blocks.
Components and Lifecycle Hooks
6. What are Angular Lifecycle Hooks?
Lifecycle hooks are methods that Angular calls at different stages of a component's life.
Common hooks include:
ngOnInit
ngOnChanges
ngDoCheck
ngAfterViewInit
ngAfterContentInit
ngOnDestroy
7. What is ngOnInit?
ngOnInit() is called once after Angular initializes component properties.
8. Difference Between Constructor and ngOnInit
| Constructor | ngOnInit |
|---|---|
| Used for dependency injection | Used for initialization logic |
| Called before Angular lifecycle | Called after component initialization |
9. What is ngOnDestroy?
It is used for cleanup operations such as unsubscribing from Observables and removing event listeners.
10. What is View Encapsulation?
View Encapsulation controls how component styles affect the DOM.
Types:
Emulated (default)
ShadowDom
None
Data Binding
11. What is Data Binding?
Data binding synchronizes data between the component and the view.
12. Types of Data Binding
Interpolation
Property Binding
Event Binding
Two-Way Binding
13. What is Interpolation?
<h1>{{ title }}</h1>
Used to display component data inside templates.
14. What is Property Binding?
<img [src]="imageUrl">
Used to bind DOM properties.
15. What is Event Binding?
<button (click)="save()">
Used to listen to user events.
16. What is Two-Way Data Binding?
<input [(ngModel)]="username">
Allows data to flow in both directions.
Directives
17. What are Directives?
Directives extend HTML functionality.
18. Types of Directives
Component Directives
Structural Directives
Attribute Directives
19. What is *ngIf?
Conditionally displays elements.
<div *ngIf="isLoggedIn">
20. What is *ngFor?
Used for looping through collections.
<li *ngFor="let user of users">
21. What is trackBy?
Improves rendering performance when using ngFor.
22. What is ngClass?
Dynamically applies CSS classes.
23. What is ngStyle?
Dynamically applies inline styles.
24. How do you create a custom directive?
Create a directive using:
ng generate directive directive-name
25. Difference Between Structural and Attribute Directives
Structural directives change DOM layout, while attribute directives modify element behavior.
Dependency Injection
26. What is Dependency Injection?
A design pattern that supplies dependencies automatically.
27. Why is DI Important?
Better code organization
Easier testing
Reduced coupling
28. What is an Injector?
An injector creates and provides service instances.
29. What are Providers?
Providers tell Angular how to create dependencies.
30. What is Hierarchical DI?
Angular creates injectors in a tree structure.
Services and RxJS
31. What is a Service?
A reusable class that contains business logic.
32. Why Use Services?
To share data and logic across components.
33. What is RxJS?
A library for reactive programming using Observables.
34. What is an Observable?
A stream of asynchronous data.
35. Difference Between Promise and Observable
| Promise | Observable |
|---|---|
| Single value | Multiple values |
| Not cancellable | Cancellable |
| Executes immediately | Lazy execution |
36. What is a Subject?
A special Observable that allows multicasting.
37. What is BehaviorSubject?
Stores and emits the latest value to new subscribers.
38. What is ReplaySubject?
Replays previous values to new subscribers.
39. What are RxJS Operators?
Functions used to transform streams.
Examples:
map
filter
switchMap
mergeMap
debounceTime
40. What is switchMap?
Switches to a new Observable while canceling the previous one.
Routing
41. What is Angular Routing?
Allows navigation between views.
42. What is RouterModule?
Provides routing functionality.
43. What is Lazy Loading?
Loads modules only when required.
44. Benefits of Lazy Loading
Faster startup time
Better performance
Reduced bundle size
45. What are Route Guards?
Protect routes from unauthorized access.
46. Types of Route Guards
CanActivate
CanDeactivate
CanLoad
CanMatch
47. What is CanActivate?
Determines whether navigation is allowed.
48. What is CanDeactivate?
Checks before leaving a page.
49. What is Route Resolver?
Fetches data before route activation.
50. How Do You Pass Route Parameters?
this.router.navigate(['/users', id]);
Forms
51. What are Angular Forms?
Angular provides mechanisms for handling user input.
52. Types of Forms
Template-Driven Forms
Reactive Forms
53. What is FormControl?
Tracks a single form field.
54. What is FormGroup?
Groups multiple controls together.
55. What is FormArray?
Manages dynamic form controls.
56. What are Validators?
Functions used for form validation.
57. Common Validators
required
minLength
maxLength
email
pattern
58. What is patchValue()?
Updates specific form fields.
59. What is setValue()?
Updates all form controls.
60. Difference Between setValue and patchValue
setValue requires all controls, patchValue allows partial updates.
HTTP and APIs
61. What is HttpClient?
Angular service for HTTP communication.
62. How Do You Make a GET Request?
this.http.get(url);
63. How Do You Make a POST Request?
this.http.post(url, data);
64. What are HTTP Interceptors?
Middleware that modifies requests and responses.
65. Use Cases for Interceptors
Authentication
Logging
Error handling
66. How Do You Handle HTTP Errors?
Using RxJS catchError operator.
67. What is CORS?
Cross-Origin Resource Sharing controls access between domains.
68. How Do You Retry Failed Requests?
Using retry() operator.
69. How Do You Cancel Requests?
Using unsubscribe() or switchMap().
70. How Do You Implement JWT Authentication?
Store token securely and attach it through interceptors.
Advanced Angular Questions
71. What is Change Detection?
Mechanism that updates the UI when data changes.
72. What is OnPush Change Detection?
Optimizes performance by reducing checks.
73. What is Zone.js?
Tracks asynchronous operations and triggers change detection.
74. What are Pipes?
Transform displayed data.
75. What is a Custom Pipe?
A user-defined data transformation pipe.
76. Difference Between Pure and Impure Pipes
Pure pipes execute only when inputs change.
77. What is AOT Compilation?
Compiles templates during build time.
78. Benefits of AOT
Faster rendering
Smaller bundles
Better security
79. What is JIT Compilation?
Compiles templates at runtime.
80. What is Angular Universal?
Server-side rendering solution for Angular.
Angular Signals and Modern Features
81. What are Angular Signals?
Signals are Angular's reactive state management primitive introduced to simplify change detection.
82. Why Use Signals?
Better performance
Simpler state management
Reduced RxJS complexity
83. What is a Writable Signal?
A signal whose value can be changed.
84. What is a Computed Signal?
Derived state calculated from other signals.
85. What is an Effect?
Runs side effects whenever signals change.
86. What are Standalone Components?
Components that don't require NgModules.
87. Benefits of Standalone Components
Simpler architecture
Reduced boilerplate
Faster development
88. What is Server-Side Rendering (SSR)?
Rendering Angular pages on the server before sending them to the browser.
89. What is Hydration?
Reusing server-rendered HTML on the client side.
90. What are Angular Control Flow Blocks?
Modern syntax:
@if()
@for()
@switch()
Expert-Level Interview Questions
91. How Do You Optimize Angular Performance?
OnPush strategy
Lazy loading
trackBy
Signals
Tree shaking
92. How Do You Prevent Memory Leaks?
Always unsubscribe from Observables.
93. What is Tree Shaking?
Removing unused code during build.
94. What is Dynamic Component Loading?
Loading components at runtime.
95. What is State Management?
Managing application state predictably.
96. What is NgRx?
Redux-inspired state management library.
97. What is ComponentStore?
Lightweight local state management.
98. What are Micro Frontends?
Architectural style that splits large applications into smaller frontend applications.
99. What Are Angular Testing Tools?
Jasmine
Karma
Jest
Cypress
100. What Topics Should Senior Angular Developers Master?
RxJS
Signals
Change Detection
SSR
Performance Optimization
State Management
Micro Frontends
Dependency Injection Internals
Conclusion
Angular interviews increasingly focus on practical development skills rather than theoretical knowledge. While understanding components, services, forms, and routing remains essential, modern Angular interviews also emphasize Signals, Standalone Components, SSR, performance optimization, and advanced RxJS concepts.
Review these 100 Angular interview questions regularly, practice coding challenges, and build real-world Angular projects to improve your confidence and increase your chances of landing your next Angular developer role.
