Question 1

What is Angular and what are its key features?

Accepted Answer

Angular is a TypeScript-based web application framework developed by Google. Its key features include components, directives, services, dependency injection, routing, forms, HTTP client, pipes, and testing support. Angular uses a component-based architecture and provides tools for building scalable, maintainable web applications.

Question 2

Explain the difference between AngularJS and Angular.

Accepted Answer

AngularJS and Angular are fundamentally different frameworks. AngularJS uses MVC architecture with two-way data binding and JavaScript, while Angular uses component-based architecture with TypeScript and one-way data flow. Angular offers better performance, mobile support, and modern development features. The transition from AngularJS to Angular requires significant changes due to architectural differences.

Question 3

What are Angular components and how do they work?

Accepted Answer

Angular components are the basic building blocks of Angular applications, combining template, styles, and logic. They use the @Component decorator to define metadata and can communicate through @Input and @Output decorators. Components have a lifecycle with hooks like ngOnInit and ngOnDestroy. Best practices include keeping components small, using the smart/dumb pattern, and implementing OnPush change detection.

Question 4

Explain Angular's dependency injection system.

Accepted Answer

Angular's dependency injection system manages dependencies between different parts of an application. Services are typically provided at the root level using @Injectable({ providedIn: 'root' }). The DI system supports different types of providers (class, value, factory) and uses hierarchical injectors. It promotes loose coupling and makes testing easier by allowing mock implementations to be injected.

Question 5

What are Angular directives and how do they work?

Accepted Answer

Angular directives are markers on DOM elements that tell Angular to attach specific behavior to those elements. There are three types: components (directives with templates), structural directives (modify DOM layout), and attribute directives (change appearance/behavior). Built-in directives include *ngIf, *ngFor, [ngClass], and [ngStyle]. Custom directives can be created using the @Directive decorator and are useful for creating reusable DOM manipulation logic.

Question 6

Explain Angular's change detection mechanism.

Accepted Answer

Angular's change detection mechanism synchronizes the application state with the view. It runs after every async operation and can be optimized using the OnPush strategy, which only checks components when their inputs change or events occur. Change detection can be manually controlled using ChangeDetectorRef, and performance can be improved by using immutable data structures, pure pipes, and minimizing bindings.

Question 7

What are Angular pipes and how do they work?

Accepted Answer

Angular pipes transform data for display in templates. They can be built-in (date, currency, uppercase) or custom-created. Pipes can be chained and parameterized. They come in two types: pure (only run when input changes) and impure (run on every change detection). The async pipe is particularly useful for handling observables. Pipes should be kept simple and pure by default for better performance.

Question 8

Explain Angular's routing system.

Accepted Answer

Angular's routing system enables navigation between different views in a single-page application. It uses the RouterModule to define routes, which can include parameters, guards, and child routes. Navigation can be done programmatically or through template links. Routes can be lazy-loaded for better performance, and guards can be used to protect routes. The router-outlet directive is used to display routed components.

Question 9

What are Angular forms and how do they work?

Accepted Answer

Angular provides two approaches to forms: template-driven and reactive. Template-driven forms are simpler and more declarative, while reactive forms offer more control and are programmatic. Both support validation, form groups, and form submission. Reactive forms are generally preferred for complex forms as they provide better control and testability. Forms can include built-in and custom validators, and their status can be tracked (pristine/dirty, valid/invalid).

Question 10

What are Angular services and how do they work?

Accepted Answer

Angular services are singleton objects that share data and logic across components. They're typically used for data fetching, state management, and business logic. Services are created using the @Injectable decorator and are usually provided at the root level. They can use dependency injection to access other services and follow the single responsibility principle. Services are crucial for maintaining clean, maintainable code by separating concerns.

Angular Interview Questions and Answers (2025)

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Table of Contents

Top Angular Interview Questions

1. What is Angular and what are its key features?

2. Explain the difference between AngularJS and Angular.

3. What are Angular components and how do they work?

4. Explain Angular's dependency injection system.

5. What are Angular directives and how do they work?

6. Explain Angular's change detection mechanism.

7. What are Angular pipes and how do they work?

8. Explain Angular's routing system.

9. What are Angular forms and how do they work?

10. What are Angular services and how do they work?

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