Angular is one of the most popular JavaScript frameworks used for building dynamic web applications. With its continuous updates and advancements, staying up-to-date with the latest Angular interview questions and answers is crucial for both job seekers and hiring managers. Here's a comprehensive list of the top 70+ Angular interview questions and answers tailored for the year 2024:

Core Concepts:

1. What is Angular?

   • Angular is a TypeScript-based open-source framework for building web applications and SPAs (Single Page Applications) maintained by Google.

2. What are the key features of Angular?

   • Features include two-way data binding, dependency injection, directives, templates, MVC architecture, and modularization.

3. What is two-way data binding in Angular?

   • Two-way data binding in Angular automatically synchronizes data between the model and the view, allowing changes in one to reflect in the other.

4. Explain Angular CLI.

   • Angular CLI (Command Line Interface) is a command-line tool used to initialize, develop, scaffold, and maintain Angular applications.

5. What is TypeScript?

   • TypeScript is a superset of JavaScript that adds optional static typing and other features to the language.

Components and Directives:

6. What is an Angular component?

   • An Angular component is a building block of Angular applications, consisting of a template, class, and metadata.

7. Differentiate between structural and attribute directives.

   • Structural directives modify the DOM layout by adding or removing elements, whereas attribute directives change the appearance or behavior of an element.

8. Explain the lifecycle hooks in Angular.

   • Lifecycle hooks are methods that allow you to tap into the lifecycle of Angular components. Examples include ngOnInit, ngOnChanges, ngOnDestroy, etc.

9. What are Angular directives?

   • Angular directives are markers on DOM elements that tell Angular's HTML compiler (part of the framework) to attach specified behavior to that DOM element or transform the DOM element and its children.

10. What is ngFor directive used for?

    • ngFor is a structural directive used to iterate over a collection, such as an array, and create a template for each item.

Services and Dependency Injection:

11. What is a service in Angular?

    • A service in Angular is a singleton object created to encapsulate business logic, share data and functionality across components.

12. Explain Dependency Injection (DI) in Angular.

    • Dependency Injection is a design pattern in which components receive their dependencies from an external source rather than creating them themselves.

13. How do you provide a service in Angular?

    • Services are provided in Angular using the @Injectable decorator, and they can be injected into components or other services via constructor injection.

14. What is providedIn property in Angular services?

    • providedIn property in Angular services specifies the module injector for the service. It's an alternative to providing the service in the @NgModule metadata.

15. What are HTTP interceptors in Angular?

    • HTTP interceptors allow you to intercept HTTP requests and responses, transform or handle them before they are sent or received by the application.

Routing and Navigation:

16. Explain Angular Router.

    • Angular Router is a powerful library that allows you to set up navigation in Angular applications, managing application states and URLs.

17. What is lazy loading in Angular?

    • Lazy loading is a technique in Angular where modules are loaded asynchronously, improving the initial loading time of the application by loading only the required modules initially.

18. How do you handle route parameters in Angular?

    • Route parameters in Angular are handled using ActivatedRoute service to retrieve parameters from the activated route.

19. What is RouterOutlet in Angular?

    • RouterOutlet is a directive provided by the Angular Router that acts as a placeholder for the views to be inserted based on the current router state.

20. How do you guard routes in Angular?

    • Route guards in Angular are used to prevent unauthorized access to certain routes, ensuring that only authenticated users can access them.

Forms and Validation:

21. Explain template-driven forms vs. reactive forms in Angular.

    • Template-driven forms rely on directives embedded in the template, while reactive forms are model-driven and created programmatically in the component class.

22. What is form validation in Angular?

    • Form validation in Angular involves ensuring that user input meets certain criteria or constraints before the form is submitted.

23. How do you perform form validation in Angular?

    • Angular provides built-in validators such as required, minLength, maxLength, pattern, etc., and also allows custom validation using FormGroup and FormControl classes.

24. What is FormBuilder in Angular?

    • FormBuilder is a service provided by Angular for creating instances of FormGroup and FormControl programmatically, simplifying the process of building reactive forms.

25. Explain form controls and form groups in Angular forms.

    • Form controls represent individual input fields in a form, while form groups are used to group related form controls together, forming a hierarchical structure.

Pipes and Data Binding:

26. What are Angular pipes?

    • Angular pipes are used for data transformation and formatting in templates. Examples include DatePipe, UpperCasePipe, LowerCasePipe, etc.

27. Explain the async pipe in Angular.

    • The async pipe in Angular is used to subscribe to an Observable or Promise and automatically unsubscribe when the component is destroyed, handling the subscription and unwrapping the value.

28. How do you create a custom pipe in Angular?

    • Custom pipes in Angular are created by implementing the PipeTransform interface and decorating the class with the @Pipe decorator.

29. What is data binding in Angular?

    • Data binding in Angular is the automatic synchronization of data between the model and the view, allowing changes in one to be reflected in the other.

30. Differentiate between one-way and two-way data binding.

    • One-way data binding binds data from the component to the view (interpolation, property binding), while two-way data binding binds data in both directions (using ngModel).

Modules and Dependency Management:

31. What is an Angular module?

    • An Angular module is a cohesive block of code with a related set of components, directives, pipes, and services. It's used to organize an application into cohesive blocks of functionality.

32. Explain lazy loading of modules in Angular.

    • Lazy loading in Angular allows you to load modules asynchronously when needed, improving initial loading time by splitting the application into smaller bundles.

33. What is NgModule in Angular?

    • NgModule is a decorator function in Angular used to define a module along with its metadata, including declarations, imports, providers, and exports.

34. How do you import and export modules in Angular?

    • Modules are imported and exported using the imports and exports arrays in the @NgModule decorator, allowing components, directives, pipes, and services to be shared across modules.

35. What is the difference between declarations, providers, and imports in NgModule metadata?

    • Declarations specify the components, directives, and pipes belonging to the module, providers specify the services available to the module, and imports specify the modules that should be imported.

Testing in Angular:

36. What are TestBed and ComponentFixture used for in Angular testing?

    • TestBed is used to configure and create an Angular testing module, while ComponentFixture is used to interact with and test components within a TestBed environment.

37. Explain unit testing in Angular.

    • Unit testing in Angular involves testing individual units of code, such as components, services, or pipes, in isolation to ensure they behave as expected.

38. What is Karma in Angular testing?

    • Karma is a test runner used for executing unit tests in Angular applications. It launches browsers, runs tests, and reports results back to the developer.

39. What is Protractor?

    • Protractor is an end-to-end testing framework for Angular and AngularJS applications. It simulates user interactions with the application and verifies that the application behaves as expected.

40. How do you mock dependencies in Angular tests?

    • Dependencies can be mocked in Angular tests using Jasmine spies or by providing mock implementations using TestBed.configureTestingModule.

Angular Performance:

41. Explain Angular Ivy.

    • Angular Ivy is the new rendering engine introduced in Angular version 9, aimed at improving performance, bundle size, and compilation times.

42. What are Angular Universal and Angular Ivy?

    • Angular Universal is a technology used for server-side rendering (SSR) of Angular applications, while Angular Ivy is the new rendering engine that powers Angular applications.

43. How do you improve Angular application performance?

    • Performance optimization techniques in Angular include lazy loading, minification, tree shaking, AOT compilation, code splitting, and optimizing change detection.

44. What is Change Detection in Angular?

    • Change detection in Angular is the process of detecting changes in the application's data model and updating the DOM to reflect those changes.

45. Explain OnPush change detection strategy.

    • OnPush is a change detection strategy in Angular where the framework checks for changes only if the input properties of a component change, improving performance by reducing unnecessary checks.

Angular CLI and Development Tools:

46. What are Angular Schematics?

    • Angular Schematics are code generators built into the Angular CLI used to scaffold components, modules, services, etc., following predefined templates and conventions.

47. Explain ng add and ng update commands in Angular CLI.

    • ng add is used to add new libraries or packages to an Angular project, while ng update is used to update the existing packages to their latest versions.

48. What is ng lint used for?

    • ng lint is a command in Angular CLI used to lint the Angular project using TSLint or ESLint, enforcing coding standards and best practices.

49. What is Angular DevTools?

    • Angular DevTools is a browser extension available for Chrome and Firefox that provides debugging and profiling tools for Angular applications, allowing developers to inspect components, performance, and state.

50. How do you debug Angular applications?

    • Angular applications can be debugged using browser developer tools, Augury extension, Angular DevTools, logging, and breakpoints in IDEs like Visual Studio Code.

Angular Security:

51. Explain Cross-Site Scripting (XSS) and how to prevent it in Angular.

    • Cross-Site Scripting (XSS) is a security vulnerability where attackers inject malicious scripts into web pages viewed by other users. In Angular, XSS is prevented by sanitizing user input using DomSanitizer or by using Angular's built-in security features.

52. What are Angular Guards and how do you use them for authorization?

    • Angular Guards are used to control access to certain routes or functionality in Angular applications. They can be used for implementing authentication and authorization logic.

53. How do you handle authentication in Angular applications?

    • Authentication in Angular applications can be handled using services like AngularFire, JWT tokens, OAuth/OIDC providers, and interceptors for adding authentication headers to HTTP requests.

54. What is Content Security Policy (CSP) and how does it relate to Angular?

    • Content Security Policy (CSP) is an added layer of security that helps detect and mitigate certain types of attacks, such as XSS. Angular applications can specify CSP directives in their index.html file to enforce security policies.

55. How do you prevent CSRF attacks in Angular?

    • Cross-Site Request Forgery (CSRF) attacks can be prevented in Angular by using CSRF tokens, same-site cookies, and ensuring that sensitive operations are protected by server-side validation.

Angular and Other Technologies:

56. Explain Angular Material.

    • Angular Material is a UI component library for Angular applications that provides a set of reusable and accessible UI components following the Material Design guidelines.

57. What is Angular Universal?

    • Angular Universal is a technology used for server-side rendering (SSR) of Angular applications, improving performance and SEO by rendering pages on the server before sending them to the client.

58. How do you integrate Angular with other libraries or frameworks?

    • Angular can be integrated with other libraries or frameworks using Angular Elements, Angular Ivy, Angular Zone.js, and by wrapping third-party libraries as Angular components.

59. What is the Angular Ivy engine?

    • Angular Ivy is the new rendering engine introduced in Angular version 9, focused on improving performance, bundle size, and compilation times.

60. Explain Angular and Redux integration.

    • Angular applications can integrate with Redux, a predictable state container for JavaScript apps, using libraries like ngRedux or ngx-redux, enabling centralized state management.

Miscellaneous:

61. What are Angular decorators?

    • Angular decorators are functions that modify the behavior of classes or properties in Angular applications, such as @Component, @Directive, @Injectable, etc.

62. What is Angular AOT compilation?

    • Ahead-of-Time (AOT) compilation in Angular compiles Angular components and templates at build time, resulting in smaller bundle sizes and faster rendering in the browser.

63. Explain Angular Zones.

    • Zones in Angular are execution contexts used to intercept and monitor asynchronous tasks in the application, such as setTimeout, XMLHttpRequest, and Promise.

64. What are Angular Elements?

    • Angular Elements allow you to package Angular components as custom elements (web components), which can be used in non-Angular applications or frameworks.

65. What is Angular Ivy renderer?

    • Angular Ivy is the new rendering engine introduced in Angular version 9, replacing the previous View Engine, aimed at improving performance, bundle size, and compilation times.

Angular Versions:

66. What are the key features introduced in Angular 12?

    • Angular 12 introduced features like stricter type checking, improved ngDevMode, Webpack 5 support, automatic font inlining, and performance improvements.

67. How does Angular 13 differ from Angular 12?

    • Angular 13 introduced improvements to the Angular compiler, stricter type checking, support for TypeScript 4.5, and updates to Angular Material components.

68. What are the new features in Angular 14?

    • Angular 14 introduced updates to Angular Material components, improved support for TypeScript 4.6, stricter type checking, and performance enhancements.

69. What is the Angular Long-Term Support (LTS) policy?

    • Angular LTS releases receive support and updates for 18 months, providing stability and security updates for enterprise applications.

70. How do you upgrade an Angular application to a newer version?

    • Angular applications can be upgraded to newer versions using the Angular CLI and following the migration guides provided by the Angular team, ensuring compatibility with the latest features and improvements.

In conclusion, mastering Angular involves understanding its core concepts, components, directives, services, routing, forms, testing, performance optimization, security, integration with other technologies, and staying updated with the latest features introduced in each version. By familiarizing yourself with these Angular interview questions and answers, you'll be well-prepared to tackle Angular-related interviews in 2024 and beyond.

Frequently Asked Questions (FAQs) for Angular Interview Preparation:

1. What is Angular?

   • Angular is a TypeScript-based open-source framework for building web applications and SPAs (Single Page Applications) maintained by Google.

2. What are the key features of Angular?

   • Angular offers features like two-way data binding, dependency injection, directives, templates, MVC architecture, and modularization.

3. How do I start with Angular?

   • To start with Angular, you can follow the official documentation and tutorials provided by Angular.io. Additionally, practicing coding exercises and building small projects can help reinforce your understanding.

4. What is the latest version of Angular?

   • As of 2024, the latest version of Angular is Angular 14. However, it's important to stay updated with the latest releases as Angular undergoes frequent updates.

5. What are the key differences between AngularJS and Angular?

   • AngularJS (1.x) is the older version of Angular, while Angular (2 and above) is a complete rewrite of the framework. Angular offers improved performance, modularity, and features like two-way data binding compared to AngularJS.