Angular Interview Questions

Angular has firmly established itself as one of the leading frameworks for building dynamic web applications. In 2023, Angular was the second most popular front-end framework amongst 90,000 developers. With its comprehensive infrastructure and robust features designed to facilitate the development of complex applications, Angular has garnered a dedicated following among developers. 

As a result, proficiency in Angular has become a sought-after skill in the tech industry, with salaries on average of $97,584 per year. In this article, we delve into some of the most pertinent Angular interview questions that can help candidates prepare effectively and stand out in their interviews.

Preparing for an Angular Interview

Successfully navigating an Angular interview requires a blend of theoretical knowledge, practical experience, and a deep understanding of Angular’s core principles and features. Used by more than 30,000 websites, Angular continues to be a popular framework for developing scalable and dynamic web applications. Interviewers are looking for candidates who not only grasp the basics but also demonstrate proficiency in advanced concepts and best practices.

Preparing for an Angular interview involves revisiting the framework’s fundamentals, such as components, services, and modules, while also diving into complex topics like reactive forms, routing, and state management. Equally important is the ability to articulate how Angular fits within the broader context of custom web development and how its features can be leveraged to solve real-world problems. By thoroughly understanding these aspects, candidates can approach their Angular interviews with confidence, ready to showcase their skills and insights.

Top 15 Angular Interview Questions

1. What is Angular, and how does it differ from AngularJS?

Angular is a platform and framework for building single-page client applications using HTML and TypeScript. AngularJS, on the other hand, is the first version of Angular which uses JavaScript. The main difference is that Angular (versions 2 and above) is entirely rewritten and includes more language choices for building applications, improved dependency injection, better performance, and more mobile support.

2. Can you explain the concept of a component in Angular?

In Angular, a component is a fundamental building block of the UI. It controls a patch of screen called a view. A component consists of a TypeScript class that encapsulates data and the logic behind it, an HTML template that declares what renders on the page, and CSS styles that define the appearance.

3. What are services in Angular, and how do they differ from components?

Services in Angular are singleton objects that are used for organizing and sharing code across your app. Unlike components, which are primarily used to build the UI, services are meant to hold business logic, data access, or code that needs to be shared across components. Services are injected into components through dependency injection, promoting code modularity and reuse.

4. Describe the Angular application architecture.

Angular applications follow a modular architecture. At the core is the Angular module, which groups together components, services, directives, pipes, and other related code into cohesive blocks. Each Angular application has at least one Angular module, known as the root module. The architecture also includes templates, directives, data binding, services, dependency injection, and routing to support complex app functionalities.

5. How does data binding work in Angular?

Data binding in Angular is a mechanism for coordinating parts of a template with parts of a component. Angular supports one-way binding (from component to template or from template to component) and two-way binding. It uses special syntax in the template HTML to achieve this, such as {{value}}, [property]=”value”, (event)=”handler”, and [(ngModel)]=”value” for two-way binding.

6. What are directives in Angular, and can you name a few types?

Directives in Angular are classes that add additional behavior to elements in your Angular applications. There are three types of directives: components (directives with a template), structural directives (change the DOM layout by adding and removing DOM elements, e.g., *ngIf, *ngFor), and attribute directives (change the appearance or behavior of an element, component, or another directive, e.g., ngStyle, ngClass).

7. Explain the difference between Constructor and ngOnInit in Angular.

The constructor is a default method of the class that is executed when the class is instantiated, and is used primarily for initializing class members. ngOnInit is a lifecycle hook in Angular, called after the constructor and used to perform initialization tasks for the component, such as fetching data from a backend service.

8. How do you create a new Angular project using Angular CLI?

To create a new Angular project, you use the Angular CLI command ng new <project-name>. This command creates a directory with the project name, installs the necessary Angular npm packages and other dependencies, and creates a simple default application.

9. What is dependency injection in Angular, and why is it important?

Dependency injection (DI) in Angular is a design pattern in which a class requests dependencies from external sources rather than creating them. DI is important because it promotes decoupling, increases modularity, and makes testing easier by allowing mock dependencies to be injected in tests.

10. Can you explain what Observables are and how they differ from Promises?

Observables provide support for passing messages between parts of your application. They are used extensively in Angular for asynchronous operations. Unlike Promises, which can only handle a single event, Observables are stream-based and can handle multiple events over time, making them more powerful for managing complex asynchronous data flows.

11. What is routing in Angular, and how do you configure it?

Routing in Angular is the process of navigating between different views or components based on user actions or URL changes. It is configured using the RouterModule and defining routes in an AppRoutingModule. Routes are defined as an array of objects, with each object specifying a path and the component to display.

Reactive forms are more scalable, robust, and suitable for complex scenarios. They are defined in the component class, which gives you more control over form behavior.

12. How can you handle forms in Angular?

Angular provides two approaches for handling forms: template-driven forms and reactive forms. Template-driven forms are suitable for simple scenarios and use directives in the template.

13. Explain the concept of lazy loading in Angular.

Lazy loading is a design pattern in Angular that allows for the loading of JavaScript components asynchronously when a specific route is activated rather than at launch. This approach can significantly reduce the initial load time of the application, enhancing performance and user experience by only loading the components necessary for the view being accessed.

14. What is Angular Material, and how can it be used?

Angular Material is a collection of Material Design components for Angular. It provides a wide range of reusable UI components like buttons, inputs, navigation patterns, and data tables, following the Material Design guidelines. Angular Material can be used by installing the package @angular/material and importing the desired modules into your Angular application to utilize these components effortlessly.

15. How do you manage state in Angular applications?

State management in Angular can be handled in various ways, including services with BehaviorSubject, using the Angular Router to preserve state, or external libraries like NgRx or Akita. These libraries provide a more structured approach to managing state, based on the Redux pattern, which involves storing the entire state of the application in a single immutable data structure.

Conclusion

Mastering Angular requires an understanding of its comprehensive ecosystem, from core concepts like components and services to advanced topics such as lazy loading and state management. The interview questions provided in this article cover a broad spectrum of Angular’s capabilities and are designed to assess a candidate’s proficiency with the framework. 

Whether you’re preparing for an Angular interview or looking to assess potential candidates, these questions offer a solid foundation for evaluating knowledge and expertise in Angular. Explore Flatirons’ custom web development services to elevate your web projects to new heights.

FAQs

How important is TypeScript knowledge for Angular development?

TypeScript knowledge is crucial for Angular development, as Angular is built on TypeScript. It provides static typing, class-based objects, and interfaces, among other features that enhance code quality and development experience.

Can Angular be used for mobile app development?

Yes, Angular can be used for mobile app development, particularly when paired with frameworks like Ionic or NativeScript, which allow for the development of hybrid mobile apps.

What’s the best way to stay updated with Angular changes?

The best way to stay updated is to follow the official Angular blog, engage with the Angular community on platforms like GitHub, Stack Overflow, and Reddit, and participate in Angular conferences or meetups.

How does Angular handle security concerns such as XSS?

Angular treats all values as untrusted by default and uses DOM sanitization to protect against security risks such as cross-site scripting (XSS). It also offers developers ways to manually mark values as trusted when necessary, following best security practices.