Top 50 Angular Interview Questions and Answers

Angular is considered one of the popular choices for building dynamic web applications. Therefore before choosing to appear for the Angular interviews, it is very important to prepare for the Angular Interview questions. Whether you are an experienced Angular developer or just starting, it is crucial to familiarise yourself with the latest trends and concepts. Read more to learn about angular js certification courses.
In this blog, we have compiled a list of 50 Angular interview questions and answers that you must consider and pay attention to excel in your career as a software developer. These come with a detailed answer to help you understand the concepts better and boost your interview readiness.

1. What is Angular?

Ans: This is one of the most asked angular basic interview questions. Angular is a popular open-source JavaScript framework developed by Google for building dynamic web applications. It facilitates the creation of single-page applications (SPAs) by providing tools and features for managing data, routing, and components.

2. Explain the difference between AngularJS and Angular.

Ans: Angular Interview questions cannot be complete without this differentiation question. AngularJS is the first version of the Angular framework, while "Angular" usually refers to the later versions (starting from Angular 2 onwards). The newer versions of Angular have improved performance, enhanced modularity, and a more intuitive syntax compared to AngularJS.

3. What are the key features of Angular?

Ans: Key features form a core part of every one of the Angular Interview questions for freshers. Angular offers features like two-way data binding, dependency injection, modular architecture, directives, pipes, and a robust CLI for efficient development and testing. It provides a comprehensive set of tools for building scalable applications, including components, services, routing, forms, and HTTP modules.

4. Explain the concept of data binding in Angular.

Ans: The concept of data binding is the most common question asked in the Angular Interview Questions. Data binding in Angular allows synchronisation of data between the component and the view. There are four types of data binding: Interpolation, Property Binding, Event Binding, and Two-Way Binding. Interpolation binds data from the component to the view using double curly braces {{}}. Property Binding binds data from the component to a property of a DOM element. Event Binding allows you to respond to events triggered by DOM elements. Two-Way Binding combines Property and Event Binding for seamless data synchronisation between the view and the component.

5. What are Angular Components?

Ans: Angular Components form one of the most basic angular interview questions asked in the interviews. Components are the basic building blocks of an Angular application. They are responsible for managing the application's UI and logic. Components are classes that control a part of the user interface. They consist of a template (HTML), styles (CSS), and logic (TypeScript). Components are arranged in a hierarchical tree structure to create the application's UI.

6. How does Dependency Injection work in Angular?

Ans: Dependency Injection is a design pattern in which the dependencies of a class are provided externally rather than created within the class itself. Angular's Dependency Injection allows components and services to declare their dependencies in their constructors. The Angular Injector then provides instances of these dependencies at runtime, promoting modularity, reusability, and ease of testing.

7. Explain Angular Modules and why they are important.

Ans: Angular Modules are containers for organising components, directives, pipes, and services. They help modularise an application and manage its complexity. Modules group related functionality together, providing better separation of concerns. They also enable lazy loading, optimising application performance by loading only the necessary modules when required.

8. What is Angular CLI?

Ans: The fundamentals behind Angular CLI are always asked in the Angular interviews questions. It is a tool that automates various development tasks like creating components, modules, services, and more. It simplifies the development process by generating boilerplate code, handling configuration, and optimising production builds. It also provides commands for testing and deployment.

9. How does Routing work in Angular?

Ans: Routing in Angular allows you to navigate between different views or components without requiring a full page reload. Angular's built-in router maps URLs to specific components. When a user clicks a link or enters a URL, the router loads the corresponding component's template and updates the view.

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10. What are Angular Directives?

Ans: Directives in Angular are one of the most asked Angular interview questions. These are instructions that modify the DOM by adding behaviour to elements. Angular has three types of directives: Component Directives (create custom HTML elements), Structural Directives (modify the layout of the DOM), and Attribute Directives (change the appearance or behaviour of elements).

11. Explain Angular Template-driven forms vs. Reactive forms.

Ans: Template-driven forms are built using directives in the template, relying on two-way data binding. Reactive forms are built programmatically using FormBuilder and FormControl classes. Template-driven forms are suitable for simple forms with less complex validation. Reactive forms offer more control and flexibility, making them ideal for complex forms with dynamic validation requirements. This is again one of the best angular js interview questions.

12. How do you perform HTTP requests in Angular?

Ans: Angular provides the HttpClientModule for making HTTP requests to a server. You can use the HttpClient service to send GET, POST, PUT and DELETE, requests to a server. It also supports interceptors for manipulating requests and responses.

13. What are Angular Guards?

Ans: Angular Guards are classes that implement interfaces like CanActivate, CanDeactivate, CanLoad, and Resolve. They allow you to control access to routes based on conditions like authentication status, user roles, or data loading. This is angularjs interview questions for experienced

14. What is Change Detection in Angular?

Ans: Change Detection is the process of identifying and updating the parts of the UI that need to be modified due to changes in the application's data. Angular employs a change detection mechanism to track changes in the component's data and automatically update the view to reflect those changes.

15. How does Angular handle internationalisation (i18n)?

Ans: Angular provides built-in support for internationalisation by allowing you to translate and localise your application. By using the i18n attribute, you can mark strings for translation and create translation files for different languages. Angular CLI can extract these strings and generate translated versions of your application. This is again one of the most asked angularjs experienced interview questions.

16. Explain Angular Universal.

Ans: Angular Universal is a technology that enables server-side rendering (SSR) of Angular applications. Angular Universal allows your application to be rendered on the server side, improving initial load times, search engine optimisation, and user experience on slower devices.

17. How can you optimise Angular application performance?

Ans: Angular provides various techniques for optimising performance, such as lazy loading, Ahead-of-Time (AOT) compilation, and using ChangeDetectionStrategy. Lazy loading delays the loading of modules until they are needed. AOT compilation compiles templates during the build process, reducing the size of JavaScript files. ChangeDetectionStrategy OnPush can be used to trigger change detection only when inputs change, improving performance. This is again one of the most basic angularjs interview questions asked to the candidates.

18. What is NgZone in Angular?

Ans: NgZone is a service that triggers Angular's change detection mechanism. NgZone helps manage and optimise change detection by running tasks either inside or outside the Angular zone. Running tasks outside the zone can improve application performance.

19. Explain Angular Animations.

Ans: Another one of the most asked Angular Interview questions are Angular animations. They provide a way to create smooth and engaging animations in your application. Angular Animations allow you to define transitions and animations for component state changes. This can enhance the user experience and make the application more visually appealing.

20. What is the purpose of Angular's TestBed?

Ans: TestBed is an Angular testing utility that provides a testing environment for running unit tests on components. TestBed helps set up and configure testing modules, components, services, and other dependencies for unit testing purposes.

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21. How do you handle errors in Angular HTTP requests?

Ans: Angular's HttpClient provides mechanisms for handling errors in HTTP requests using operators like catchError. You can use the catchError operator to handle errors in observables returned by HTTP requests. This allows you to gracefully handle errors and display appropriate error messages to users. These kinds of interview questions for angularjs developer is nowadays asked often.

22. What are Angular Services?

Ans: Angular Services are classes in Angular that are responsible for handling business logic, data retrieval, and communication with APIs. Angular Services provide a way to encapsulate and share functionality across components. They promote code reusability and separation of concerns.

23. Explain the concept of Zones in Angular.

Ans: Zones in Angular are very common Angular Interview Questions to be asked in these interviews. These are execution contexts that allow tracking asynchronous operations in an Angular application. Zones in Angular enable change detection by tracking asynchronous tasks and triggering the change detection process when tasks are completed. This helps ensure that the UI remains up to date with the application's data.

24. How can you share data between components in Angular?

Ans: Data sharing between components can be achieved through Input and Output properties, ViewChild/ViewChildren, and Angular Services. Input properties allow parent components to pass data to child components, while Output properties emit events to notify parent components of changes. ViewChild/ViewChildren can be used to access child component elements. Angular Services can store and manage shared data between components.

25. Explain Angular's Content Projection (ng-content).

Ans: Content Projection in Angular is considered one of the most frequently asked angular interview questions. It is a mechanism in Angular that allows you to project content from a parent component's template into a child component. Using the ng-content directive, you can define placeholders in a child component's template where content from the parent component can be injected. This enables the creation of reusable and flexible components.

26. What is the Angular Router Outlet?

Ans: The Angular Router Outlet is a directive that acts as a placeholder for rendering routed components. The Router Outlet is used to display the components associated with specific routes. It dynamically loads and displays components based on the route configuration.

27. How can you optimise lazy-loaded modules in Angular?

Ans: When the talk is about angularjs programming interview questions then one cannot miss this. Lazy-loaded modules can be optimised by using the PreloadAllModules strategy and the CanLoad guard. The PreloadAllModules strategy preloads all lazy-loaded modules in the background to improve navigation speed. The CanLoad guard prevents the loading of a module if certain conditions are not met, enhancing the application's security and performance.

28. Explain ng-container in Angular.

Ans: ng-container is a structural directive in Angular that doesn't create a DOM element. It is often used for conditionally rendering content. ng-container provides a way to group and manipulate elements without introducing unnecessary elements into the DOM. It is useful for scenarios where you want to apply directives to a section of the template without affecting the layout.

29. How do you handle forms validation in Angular?

Ans: Angular provides both template-driven and reactive approaches to form validation using built-in validators and custom validators. Template-driven forms use template-driven directives like ngModel and built-in validators like required and pattern. Reactive forms use FormControl and FormGroup classes along with custom validation functions for more complex validation scenarios.

30. Explain Angular's View Encapsulation.

Ans: This Angular Interview questions and answers for experienced professionals plays a greater part in the angular interview. Therefore, angular ViewEncapsulation is an Angular feature that controls how styles are encapsulated and applied to components. Angular supports three types of ViewEncapsulation: Emulated (default), Native, and None. Emulated encapsulation uses shadow DOM or similar techniques to encapsulate styles. Native encapsulation relies on browser-native shadow DOM. None encapsulation doesn't encapsulate styles, allowing them to bleed into other components.

31. What is the purpose of Angular's ngOnInit lifecycle hook?

Ans: The ngOnInit lifecycle hook in Angular is used to perform initialisation tasks for a component after Angular has initialised the component's data-bound properties. It is a good place to perform setup operations such as fetching data from a server, initialising variables, or setting up subscriptions. It is called once after the component's inputs are bound but before the view is rendered.

32. Explain the concept of Observables and RxJS in Angular.

Ans: Observables are a part of the Reactive Extensions for JavaScript (RxJS) library and are widely used in Angular for handling asynchronous operations and data streams. Observables represent a sequence of values over time and can emit values, errors, and completion notifications. They provide powerful tools for working with asynchronous data, handling events, and managing data flow. This is one of the most notable angular js interview questions.

33. How can you handle route parameters in Angular?

Ans: Angular's ActivatedRoute service is used to access route parameters. You can extract route parameters using the params property of ActivatedRoute. For example, if you have a route such as /user/:id, you can access the id parameter using this.route.snapshot.params.id. Additionally, you can subscribe to the params observable to handle changes to route parameters dynamically.

34. What are Angular Pipes and how do they work?

Ans: Angular Pipes are used to transform data in templates before displaying it. They take input data and return transformed output. Pipes are used for operations such as formatting dates, currency conversion, uppercase/lowercase transformations, and more. Pipes are used within double curly braces {{}} in templates, and you can also chain multiple pipes together.

35. What is the purpose of Angular's ng-template?

Ans: One of the most asked Angular Interview Questions is this question where the purpose of Angular’s ng-template is asked. ng-template is an Angular element used to define a template that can be used later without rendering it immediately. It is often used in conjunction with structural directives such as ngIf, ngFor, and ngSwitch to conditionally render or iterate over elements without adding extra elements to the DOM. It is particularly useful for creating reusable templates.

36. How do you implement lazy loading in Angular?

Ans: Lazy loading is achieved by loading modules only when they are needed, reducing the initial load time of an application. To implement lazy loading in Angular, you can define a separate module for each feature or route and use the loadChildren property in the route configuration to specify the path to the module file.

37. Explain the concept of Angular Interceptors.

Ans: Angular Interceptors are used to intercept HTTP requests and responses globally in an Angular application. They provide a way to modify requests or responses, add headers, handle errors, and perform other tasks before they reach the server or after they leave the server. Interceptors are particularly useful for implementing authentication, logging, or caching logic. This is one of the most notable angularjs interview questions for experienced candidates.

38. What is the difference between ngFor and ngIf directives in Angular?

Ans: ngFor is a structural directive used for iterating over a collection and generating HTML elements based on the data. It repeats a portion of the template for each item in the collection. ngIf, on the other hand, is a structural directive used for conditionally rendering elements based on a boolean expression. It controls whether an element is added to the DOM or not.

39. How do you share data between sibling components in Angular?

Ans: Data sharing between sibling components can be achieved through a shared service. The service acts as a mediator between the components, allowing them to communicate and share data. Components can inject the shared service and use its methods and properties to exchange data.

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40. What is Angular's trackBy function used for in ngFor?

Ans: This is one of the most asked Angular Interview Questions for experienced professionals. The trackBy function is used in conjunction with ngFor to improve the performance of rendering lists with dynamic data. By default, Angular tracks array items by their identity (memory reference). By providing a trackBy function, you can specify a unique identifier for each item in the list. This helps Angular to re-render only items that have changed, reducing unnecessary DOM updates.

41. Explain the concept of Angular's ChangeDetectionStrategy OnPush.

Ans: ChangeDetectionStrategy.OnPush is an optimisation strategy for change detection in Angular. When this strategy is used, Angular only triggers change detection for a component when its input properties change or an event bound to the component is fired. This can significantly improve the performance of an application by reducing unnecessary change detection cycles.

42. How do you perform unit testing for Angular components?

Ans: Angular provides tools such as TestBed and Jasmine for unit testing components. You can create a test bed environment using TestBed.configureTestingModule, configure the testing module with necessary dependencies, and use Jasmine's testing functions such as describe, beforeEach, and it to write test cases. You can use TestBed.createComponent to create instances of your components for testing and use TestBed.inject to get instances of services.

43. What is ngZone.run() in Angular and why is it used?

Ans: ngZone.run() is a method provided by the NgZone service in Angular. It allows you to execute a function inside or outside the Angular zone. When code is run inside the Angular zone, it triggers change detection. By running code outside the zone, you can prevent unnecessary change detection and improve performance for specific tasks. This is again one of the most asked angularjs experienced interview questions.

44. How do you handle form submissions and HTTP requests together in Angular?

Ans: To handle form submissions and HTTP requests together, you can use the HttpClient service to send POST or PUT requests to the server with the form data as the request body. You can also handle validation and error scenarios by subscribing to the observable returned by the HTTP request and displaying appropriate messages to the user.

45. Explain the concept of Angular's ViewChild and ViewChildren.

Ans: One of the frequently asked Angular Interview questions and answers is this question. @ViewChild and @ViewChildren are decorators used to access child elements or components from the parent component. @ViewChild allows you to get a reference to a single element or component, while @ViewChildren provides a reference to multiple elements or components of the same type. This enables interaction and communication between parent and child components.

46. What is AOT compilation in Angular and why is it important?

Ans: Ahead-of-Time (AOT) compilation is a process in which Angular compiles templates and components during the build phase rather than at runtime. AOT compilation produces smaller and more efficient JavaScript code, eliminates the need for a just-in-time (JIT) compiler in the browser, and reduces the initial loading time of an application.

47. How can you secure Angular applications and prevent cross-site scripting (XSS) attacks?

Ans: To secure Angular applications against cross-site scripting (XSS) attacks, use Angular's built-in data binding, which automatically escapes potentially dangerous content. Also, sanitise user-generated content using the DomSanitiser service before rendering it in the template. Avoid using unsafe APIs or directly manipulating the DOM.

48. What is the purpose of the ng-content select attribute?

Ans: The ng-content select attribute is used to select specific content projection slots when using content projection (transclusion) in Angular. It allows you to project content into different slots based on the selector provided. This is particularly useful when a component has multiple ng-content placeholders and you want to target a specific one. These kinds of angular interview questions are asked frequently.

49. Explain the role of Angular's ngDoCheck lifecycle hook.

Ans: ngDoCheck is a lifecycle hook in Angular that is called whenever Angular detects changes in the component's data, whether due to a change in its input properties, a change in the components it uses, or other factors. It is a good place to implement custom change detection logic or perform actions based on changes that Angular's default change detection might not catch.

50. How can you achieve dynamic theming in an Angular application?

Ans: One of the commonly asked Angular advanced interview questions is dynamic theming in an Angular application. Dynamic theming in Angular can be achieved using CSS variables (custom properties) or a theme service. CSS variables allow you to define colour and style values at the root level and apply them throughout the application. Alternatively, a theme service can dynamically update the application's styles based on user preferences or application settings.

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Conclusion

Utilising these Angular interview questions and understanding their detailed answers will undoubtedly give you a competitive edge during your job interviews. These will help you give a competitive edge to the top in all your angular interviews. From basic to angular advanced interview questions, these fundamentals listings of questions will surely open the doors for you to be a successful software developer.

These not only provide you with a theoretical framework but also a practical approach to dealing with the angular topic. And also remember these practical experiences and hands-on projects play a significant role in enhancing your Angular skills, so make sure to put your knowledge into practice and explore real-world scenarios to solidify your expertise.