Top 25 AngularJS Interview Questions and Answers

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Angular is a popular web framework that has been gaining traction among developers worldwide. According to a recent survey, Angular is the 5th most used web framework among software developers worldwide, with 17.46% of respondents using it. This web framework is known for its excellent performance, scalability, and features like built-in testing tools. It is maintained by Google and is in high demand because it helps create great user interfaces across different industries. Knowing Angular well is important for developers because of its growing popularity. If you’re looking for an Angular job, you might find this blog post useful. This guide covers the top 25 Angular interview questions and answers to help you prepare with confidence. 

Basic Level Angular Questions for Interview

Here are some basic level Angular interview questions and answers:

1. What is Angular?

Angular is a powerful front-end framework developed by Google for building dynamic web applications. It’s based on TypeScript and offers a structured approach to crafting interactive user interfaces.

As a comprehensive framework, it manages various facets of front-end web development, including handling HTTP requests, layout, forms, routing, validation, reactivity, and more.

2. What is the difference between AngularJS and Angular?

AngularJS is an open-source front-end framework rooted in JavaScript, widely employed for crafting single-page web applications. 

On the other hand, Angular, devised by Google, is a prominent platform and an open-source web application framework that utilizes TypeScript. 

The primary differences between AngularJS and Angular lie in their architecture, language, and approach to building applications: 

AngularJS	Angular
Based on MVC architecture	Based on Service/Controller
Uses JavaScript	Utilizes TypeScript for application building
Lacks mobile platform support	Fully supports mobile platforms
Built on controllers	Embraces a component-based UI approach
Challenging for SEO-friendly applications	Simplifies building SEO-friendly applications

3. What is TypeScript?

TypeScript is a programming language developed by Microsoft. It’s a superset of JavaScript, meaning it includes all JavaScript features but adds extra capabilities on top. TypeScript introduces static typing, enabling developers to define types for variables, functions, and more. 

This helps catch errors during development and enhances code reliability. It also supports modern JavaScript features and allows for better tooling, making it easier to manage larger codebases and collaborate on projects. 

4. What are the key components of Angular?

Angular comprises several key components essential for its structure:

• Components: These serve as the fundamental units governing HTML views within an Angular application.

• Modules: Angular modules assemble various basic building blocks like components, directives, and services. They logically divide an application into manageable pieces, each dedicated to a specific task.

• Services: These facilitate the creation of shareable components usable across the entire Angular application, enhancing reusability and maintainability.

• Templates: Templates in Angular represent the views, providing the structure for how information is displayed within the application.

• Metadata: Used to supplement Angular classes with additional data, enriching their functionality within the application architecture.

5. What is data binding? Which type of data binding does Angular deploy?

Data binding enables users to manipulate webpage elements through a web browser without requiring intricate scripting or programming. It leverages dynamic HTML, particularly useful in web pages housing interactive components like forms, calculators, tutorials, and games. 

Angular employs two-way binding, synchronizing changes between the user interface and the corresponding model state. This bidirectional approach ensures that alterations in the UI are reflected in the model state and vice versa. 

By linking the DOM to the Model data via the controller, Angular facilitates this connection. However, this approach can impact performance as it necessitates tracking every DOM change.

Angular JavaScript Interview Questions for Freshers

Here are some important Angular interview questions and answers for freshers:

6. What are Directives in Angular?

Directives in Angular serve as attributes enabling users to create custom HTML syntax tailored to their applications. When detected in the DOM by the Angular compiler, directives execute their defined functionalities. Angular encompasses three primary types of directives:

• Component Directives: These directives encapsulate templates, logic, and styles, creating reusable custom elements in the application.

• Attribute Directives: Attribute directives alter the behaviour or appearance of DOM elements, allowing developers to add, modify, or remove attributes or behaviour.

• Structural Directives: These directives modify the layout by manipulating the DOM’s structure, altering the display based on conditions like loops or conditional statements.

7. What are the technologies used in Angular?

Angular harnesses several pivotal technologies to streamline and enhance the development process:

• TypeScript: It serves as Angular’s primary programming language, offering strong typing and modern features.

• Zone.js: This JavaScript library enables Angular to track and manage changes within the application state by establishing execution contexts known as “zones”.

• RxJS: This library, known as Reactive Extensions for JavaScript, manages asynchronous data flow and event handling using observables.

• Angular CLI: The Angular Command Line Interface (CLI) is a robust tool enabling the generation, building, testing, and deployment of Angular applications.

• Dependency Injection: Angular employs a hierarchical Dependency Injection (DI) system, offering instances of classes, services, or values to components and services, facilitating efficient communication and reusability.

• Angular Material: This UI component library provides a collection of high-quality, accessible, and modular UI components adhering to the Material Design principles, enhancing the user interface and experience.

8. What is the purpose of the async pipe?

The async pipe serves to identify components requiring change detection. It subscribes to an Observable or Promise, presenting the latest emitted value. Upon emitting a new value, the async pipe flags the components. 

It autonomously detaches or unsubscribes when a component is destroyed. Moreover, if the component’s expression reference changes, the async pipe unsubscribes from the previous Observable or Promise and subscribes to the updated one.

9. What is an AOT compilation? What are its advantages?

The Ahead-of-time (AOT) compiler transforms Angular’s HTML and TypeScript code into JavaScript before the code reaches the browser, occurring in the build phase.

Benefits of AOT include:

• Speedier Rendering: Accelerated initial rendering of applications.
• Compact Framework Size: Decreased download size for the Angular framework.
• Reduced Async Requests: Fewer asynchronous requests, optimizing performance.
• Enhanced Security: Improved security measures for the application.
• Prompt Error Detection: Rapid identification of template errors.

10. What is String Interpolation in Angular?

String interpolation in Angular involves embedding variables or expressions within HTML templates using double curly braces ({{ }}). These placeholders are replaced with the corresponding component’s data, allowing seamless dynamic content display. 

It simplifies showcasing component properties, method results, or computed values directly in the rendered view, enhancing the flexibility and interactivity of the user interface.

Angular Interview Questions for Experienced 

Here are some of the most-asked Angular interview questions and answers for experienced candidates:

11. What are Angular elements? What is the browser support of Angular Elements?

Angular elements are essentially Angular components adhering to the web standard for creating custom HTML elements, also known as web components. When added to the DOM tree, these custom elements automatically trigger in an Angular context.

Angular’s foundation on modern web standards ensures compatibility with Chrome, Edge (Chromium-based), Firefox, Opera, Safari, and other modern browsers via polyfills. Polyfills are code fragments enabling modern browsers to handle features not inherently supported.

12. What are RxJs in Angular?

RxJS in Angular refers to Reactive Extensions for JavaScript, a library used to manage asynchronous data streams and handle events over time. 

It’s a core part of Angular’s reactive programming paradigm, centred around Observables—data streams that can be subscribed to and manipulated using operators. 

RxJS empowers developers to manage complex asynchronous operations, event handling, and data stream manipulation more effectively within Angular applications.

13. What is schematic?

A schematic is a template-driven code generation tool within the Angular framework that facilitates the creation, modification, and scaffolding of code and project structures. 

It’s used to automate repetitive tasks, generate boilerplate code, and transform projects efficiently by defining and applying predefined templates and operations. Schematics help streamline development workflows and maintain code consistency across Angular applications.

14. What is the role of SPA in Angular?

A Single Page Application (SPA) keeps the same index.html page despite frequent URL changes. SPA simplifies development and boosts speed compared to conventional web technologies by maintaining a single page for the application’s interface, resulting in faster loading times and smoother user experiences.

15. What are HTTP interceptors?

HTTP interceptors in Angular enable the interception of HTTP requests and responses on a global scale. They offer a centralized mechanism to preprocess or manipulate these requests and responses before reaching the server or client. 

This functionality proves beneficial for tasks like request logging, appending authentication headers, error handling, or data modification. Interceptors, registered within an Angular module, execute sequentially based on the request/response pipeline, providing a powerful means of handling HTTP operations.

AngularJS Experienced Interview Questions 

Here are some important Angular JS interview questions for experienced:

16. List out the scope characteristics in AngularJS?

The Scope object in AngularJS embodies five significant traits:

• Contextual Evaluation: Serves as a context for evaluating AngularJS expressions within the application.

• API Access: Offers APIs like $apply to propagate model modifications from controllers, services, or AngularJS event handlers into the view.

• Model Observation: Facilitates model change observation through services like $watch.

• Inherited Properties: Inherits properties from parent scopes, enabling access to shared model properties.

• Nesting Capabilities: Allows for scope nesting, creating isolation for directives and different AngularJS components.

17. Explain what a digest cycle is in AngularJS.

In each digest cycle, Angular compares new scope model values to their previous counterparts through a process known as dirty checking. When changes are detected, watches set on the new model trigger, initiating another digest cycle. This process continues until all models stabilize.

While the digest cycle typically triggers automatically, it can also be manually invoked using “.$apply()”.

18. What is dependency injection in AngularJS?

Dependency Injection (DI) is a core concept in AngularJS, allowing components to request dependencies (services or objects) from an external source rather than creating them manually. 

This pattern promotes modularity, testability, and reusability by enabling easier management of dependencies. Angular’s injector subsystem handles the injection of required dependencies into components, making it easier to maintain and test the application.

19. Differentiate between $scope and $rootScope in AngularJS.

• $scope: It is a scope object that is associated with the view and its corresponding controller. Each controller in AngularJS has its own $scope, providing an isolated scope for the view it controls. It is not directly accessible across controllers.
• $rootScope: It is the parent of all $scope objects in an AngularJS application. It exists throughout the application lifecycle, and any property or method added to $rootScope is accessible across all controllers. However, its usage should be minimal due to potential scope pollution and complexity issues.

20. Explain the role of services in AngularJS.

Services in AngularJS are singletons that encapsulate reusable business logic or utilities that can be shared across different parts of an application. 

They provide a way to keep controllers lean by moving logic and data manipulation out of the controllers and into separate, maintainable components. 

Services can include functionalities like data fetching, data manipulation, authentication, and more. Angular’s built-in services ($http, $timeout, etc.) or custom services help maintain the separation of concerns and facilitate code reuse.

Technical Angular Questions for Interview

Here are some technical Angular interview questions with answers: 

21. What is the purpose of Angular CLI, and how does it simplify Angular development?

Angular CLI (Command Line Interface) is a powerful tool designed to streamline Angular development by providing a set of commands for creating, managing, and deploying Angular applications effortlessly. 

It simplifies the setup process by generating boilerplate code, creating components, services, modules, etc., and optimizing the build process for production deployment. CLI abstracts the complex build configurations, making it easier for developers to focus on application logic rather than build tooling.

22. Describe the concept of lazy loading in Angular and its benefits.

Lazy loading is a technique used to load only necessary modules or components when they are required rather than loading the entire application upfront. In Angular, lazy loading is achieved by configuring the routing module to load modules asynchronously. 

Benefits include faster initial loading times, improved performance, reduced bandwidth usage, and better user experience, as only the essential parts of the application are loaded initially.

23. Explain the difference between ngOnChanges and ngOnInit lifecycle hooks in Angular.

• ngOnChanges: This lifecycle hook is invoked every time there is a change in an @Input property binding. It receives a SimpleChanges object that contains the previous and current values of the bound property.
• ngOnInit: This hook is called once after the first ngOnChanges and is used for initialization tasks such as retrieving data from services, initializing component properties, or subscribing to observables. It runs after Angular has initialized the component’s input properties.

24. What are Angular pipes, and give an example of their usage?

Angular pipes are used to transform data before displaying it in the view. They allow for formatting, filtering, and manipulating data in templates. 

For instance, the DatePipe can format a date object into a desired format like ‘short’, ‘medium’, ‘fullDate’, etc. Pipes can be chained together for more complex transformations. An example of usage would be:

<p>{{ today | date:’fullDate’ }}</p>

This code uses the DatePipe to format the today variable as a full date.

25. What are Angular guards, and how are they used in routing?

Angular guards are used to control the navigation flow in Angular applications. They are classes implementing specific interfaces (CanActivate, CanDeactivate, CanLoad, etc.), allowing developers to execute logic before activating or deactivating a route.

• CanActivate: Checks if a route can be activated.
• CanDeactivate: Checks if a route can be deactivated.
• CanLoad: Checks if a module can be loaded lazily. Guards are applied to routes in the routing configuration and can perform tasks like authentication, authorization, confirmation dialogs, etc., before allowing navigation to proceed.

Tips to Answer Angular Interview Questions

Follow these tips to answer Angular interview questions with confidence: 

• Understand Core Concepts

Be clear on Angular’s fundamentals, like components, modules, services, and dependency injection.

• Be Precise and Clear

Answer questions directly, avoiding unnecessary jargon or overly technical explanations.

• Show Problem-Solving Skills

Discuss how you’ve solved challenges using Angular, demonstrating problem-solving abilities.

• Stay Updated

Keep up-to-date with the latest Angular features and improvements to discuss current trends or updates.

• Ask for Clarification

If a question isn’t clear, politely ask for clarification before answering to ensure you address the intended topic.

Conclusion

Mastering Angular concepts is key to acing interviews. These top 25 Angular questions and answers offer crucial insights and help you get prepared. Looking to boost your Angular career? Visit Hirist – an online platform for the best Angular job opportunities. Grow your career in Angular development through Hirist’s diverse job listings and resources.