Angular is a powerful front-end framework developed by Google for building dynamic web applications. Its component-based architecture, dependency injection, and reactive programming capabilities make it a preferred choice for many companies, including Accenture. If you're preparing for an Angular Developer interview at Accenture, this blog covers the most commonly asked Angular interview questions and answers to help you succeed.
1. What is Angular?
Angular is a platform and framework for building single-page client applications using HTML and TypeScript. It provides a robust structure for managing web applications, with features like two-way data binding, dependency injection, and component-based architecture.
2. Explain the architecture of an Angular application.
Angular applications consist of several key components:
- Modules: Containers for a cohesive block of code.
- Components: UI building blocks with associated templates.
- Services: Classes that handle business logic and data access.
- Dependency Injection: A design pattern to achieve Inversion of Control.
- Templates: HTML views rendered by the components.
3. What are components in Angular?
Components are the fundamental building blocks of an Angular application. Each component controls a patch of the screen called a view. They consist of:
- Class: Contains the business logic.
- Template: Defines the HTML structure.
- Styles: CSS styles specific to that component.
4. What is a module in Angular?
An Angular module is a container for a cohesive block of code. It can include components, directives, services, and pipes. Every Angular application has at least one module, the root module, often named AppModule.
5. What is a service in Angular?
A service is a class that provides specific functionality that can be reused throughout the application. Services are typically used for data retrieval, business logic, and shared functionalities. They are injected into components or other services using Angular's Dependency Injection system.
6. Explain data binding in Angular.
Data binding is the mechanism that allows synchronization between the model (data) and the view (UI). Angular supports:
- One-way data binding: Data flows in one direction, either from the model to the view or vice versa.
- Two-way data binding: Changes in the model reflect in the view and vice versa (using
[(ngModel)]).
7. What are directives in Angular?
Directives are classes that add behavior to elements in your Angular applications. There are three types of directives:
- Components: Directives with a template.
- Structural Directives: Change the DOM layout (e.g.,
*ngIf,*ngFor). - Attribute Directives: Change the appearance or behavior of an element (e.g.,
ngStyle,ngClass).
8. What is the purpose of the ngIf directive?
The ngIf directive is a structural directive that conditionally includes or excludes an element from the DOM based on the truthiness of the expression provided to it.
<div *ngIf="isVisible">This is visible if isVisible is true.</div>
9. What are pipes in Angular?
Pipes are a way to transform data for display in templates. They can be used to format data, such as dates and currencies, or to filter arrays. Angular provides several built-in pipes, and you can create custom pipes as well.
<p>{{ date | date:'shortDate' }}</p>
10. What is Dependency Injection in Angular?
Dependency Injection (DI) is a design pattern used to implement IoC (Inversion of Control), allowing a class to receive its dependencies from external sources rather than creating them internally. Angular uses DI to manage services, making them available to components.
11. Explain the difference between @Component and @NgModule.
@Component: A decorator that marks a class as an Angular component, defining its metadata, including its selector, template, and styles.@NgModule: A decorator that marks a class as an Angular module, defining its declarations, imports, exports, providers, and bootstrap components.
12. What is a lifecycle hook in Angular?
Lifecycle hooks are special methods that Angular calls at specific points in a component's lifecycle. Common lifecycle hooks include:
ngOnInit(): Called after the component's view has been initialized.ngOnChanges(): Called when an input property changes.ngOnDestroy(): Called just before the component is destroyed.
13. What is routing in Angular?
Routing in Angular enables navigation from one view to another in a single-page application. It uses the RouterModule to define routes and associate them with components. The router manages the URL and loads the corresponding component when the user navigates.
14. What is the purpose of Reactive Forms in Angular?
Reactive Forms provide a model-driven approach to managing form inputs. They allow for dynamic form creation and validation, offering greater flexibility and control over form data. Reactive forms use FormGroup and FormControl to track form state.
15. How do you handle HTTP requests in Angular?
Angular provides the HttpClient module for making HTTP requests. It supports features like request and response interception, error handling, and type-safe requests.
import { HttpClient } from '@angular/common/http';
constructor(private http: HttpClient) {}
this.http.get('api/data').subscribe(data => {
console.log(data);
});
16. What is lazy loading in Angular?
Lazy loading is a technique that loads feature modules only when needed, improving the initial loading time of an application. It can be implemented using the Angular Router by configuring routes with the loadChildren property.
17. Explain the concept of ngZone.
ngZone is a service in Angular that allows you to manage the execution context and run code outside of Angular’s zone. It helps in optimizing performance by minimizing change detection cycles when handling asynchronous operations.
18. What is the purpose of the async pipe in Angular?
The async pipe subscribes to an Observable or Promise and returns the latest value it has emitted. It automatically unsubscribes when the component is destroyed, making it a convenient way to handle asynchronous data in templates.
<p>{{ data$ | async }}</p>
19. How can you create a custom directive in Angular?
To create a custom directive, use the @Directive decorator and implement the required behavior within the directive class. You can then use it in your templates as an attribute.
import { Directive, ElementRef, Renderer2 } from '@angular/core';
@Directive({
selector: '[appHighlight]'
})
export class HighlightDirective {
constructor(el: ElementRef, renderer: Renderer2) {
renderer.setStyle(el.nativeElement, 'backgroundColor', 'yellow');
}
}
20. What is the purpose of the ngModel directive?
The ngModel directive is used for two-way data binding in forms. It binds a form input to a variable in the component, allowing for automatic updates between the view and model.
<input [(ngModel)]="name" />
21. How do you implement a guard in Angular routing?
Guards are used to control access to routes. You can create a guard by implementing the CanActivate or CanDeactivate interfaces and then apply it to your routes.
@Injectable({
providedIn: 'root'
})
export class AuthGuard implements CanActivate {
canActivate(): boolean {
return this.isAuthenticated();
}
}
22. Explain the difference between Observables and Promises.
- Observables: Can emit multiple values over time, support operators for transformation and composition, and are cancellable.
- Promises: Resolve a single value or error and cannot be cancelled or modified once created.
23. What is the RouterOutlet in Angular?
RouterOutlet is a directive that acts as a placeholder in the template where the routed component gets displayed based on the current route.
24. What is the purpose of the ng-content directive?
ng-content is used for content projection in Angular, allowing you to pass content from a parent component to a child component, enabling flexible component design.
25. How can you optimize the performance of an Angular application?
Some optimization techniques include:
- Lazy loading of modules.
- Change detection strategy: Use
OnPushstrategy. - TrackBy function in
*ngForto reduce DOM manipulation. - AOT (Ahead-of-Time) compilation.
26. What is the difference between a template-driven and a reactive form?
- Template-driven forms: Use Angular directives in the template to create forms and handle validation. They are easier to set up but less flexible.
- Reactive forms: Are created in the component class using
FormGroupandFormControl, providing more control and better handling of complex validations.
27. How do you implement internationalization (i18n) in Angular?
Angular provides built-in support for internationalization through the @angular/localize package, allowing you to translate your application into multiple languages using translation files.
28. What are the different types of pipes in Angular?
Angular provides several built-in pipes, including:
- DatePipe: Formats dates.
- CurrencyPipe: Formats currency values.
- DecimalPipe: Formats numbers.
- JsonPipe: Converts an object into a JSON string.
29. What is the purpose of the trackBy function in *ngFor?
The trackBy function is used to improve performance in *ngFor by tracking the identity of items in the list, helping Angular optimize the rendering and avoid unnecessary DOM manipulations.
30. Explain the concept of routing parameters in Angular.
Routing parameters are dynamic segments in a route that allow you to pass data to the routed component. They can be accessed using ActivatedRoute in the component to get the parameters from the URL.
import { ActivatedRoute } from '@angular/router';
constructor(private route: ActivatedRoute) {}
ngOnInit() {
this.route.params.subscribe(params => {
console.log(params['id']);
});
}
Conclusion
These top 30 Angular interview questions and answers will equip you with the knowledge needed to excel in your Accenture interview. Be sure to practice your coding skills, understand the concepts, and prepare for scenario-based questions to stand out as a candidate.
Good luck!
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