Angular.js Interview Questions and Answers for 7 years experience

1. What is AngularJS and its core features?

   • Answer: AngularJS is a JavaScript-based open-source front-end web application framework mainly maintained by Google and by a community of individuals and corporations to address many of the challenges encountered in developing single-page applications. Its core features include: Model-View-Controller (MVC) architecture, data binding, dependency injection, directives, templating, routing, and testing capabilities. It simplifies development by providing a structured approach and reusable components.

2. Explain the concept of data binding in AngularJS.

   • Answer: Data binding is a key feature that synchronizes data between the model (data) and the view (UI). AngularJS offers two-way data binding, meaning changes in the model automatically reflect in the view, and vice-versa. This eliminates the need for manual DOM manipulation, simplifying development and improving maintainability.

3. What are directives in AngularJS? Give examples.

   • Answer: Directives extend HTML by adding new attributes, elements, or classes. They are used to create custom components and manipulate the DOM. Examples include `ng-model` (two-way data binding), `ng-repeat` (iterating over arrays), `ng-if` (conditional rendering), `ng-show`/`ng-hide` (conditional visibility), and custom directives created by developers.

4. Explain the concept of dependency injection in AngularJS.

   • Answer: Dependency injection is a design pattern where dependencies are provided to a component rather than created within it. This promotes modularity, testability, and reusability. AngularJS uses dependency injection to manage the lifecycle of components and their dependencies, making code cleaner and easier to maintain.

5. Describe the difference between `ng-show` and `ng-if` directives.

   • Answer: `ng-show` hides or shows an element by setting its CSS `display` property. The element remains in the DOM, just hidden. `ng-if`, on the other hand, removes or adds the element to the DOM entirely based on the condition. `ng-if` is better for performance when dealing with frequently changing conditions that affect large parts of the DOM, while `ng-show` is better for simple visibility toggles.

6. How does AngularJS handle routing?

   • Answer: AngularJS uses the `ngRoute` module (or third-party routing solutions like ui-router) to manage client-side routing. This allows developers to create single-page applications with multiple views, navigating between them without requiring full page reloads. Routes are configured using the `$routeProvider` service, defining URLs and the associated views (templates and controllers).

7. What are scopes in AngularJS?

   • Answer: Scopes are objects that act as bridges between the model and the view. They hold application data and provide methods that the view can use to interact with the data. Scopes are hierarchical, allowing for efficient data management in complex applications. The root scope is associated with the `$rootScope`.

8. Explain the concept of controllers in AngularJS.

   • Answer: Controllers are JavaScript functions that are associated with a specific view (template). They manage the data and logic for that view, handling user interactions and updating the model. They are responsible for the behavior and presentation of the view.

9. What are services in AngularJS and how are they used?

   • Answer: Services are reusable components that perform specific tasks, such as accessing data from a server, performing calculations, or validating input. They are typically created using factory or service patterns and are injected into controllers and other components as needed. This promotes modularity and reusability.

10. How do you handle asynchronous operations in AngularJS (e.g., HTTP requests)?

    • Answer: AngularJS uses promises and the `$http` service to handle asynchronous operations. The `$http` service makes AJAX requests, returning a promise that resolves or rejects based on the request's success or failure. The `then()` method is used to handle the resolved promise, while `catch()` handles rejection.

11. Explain the difference between a factory and a service in AngularJS.

    • Answer: Both factories and services are used to create reusable components, but they differ in how they are defined. A factory is a function that returns an object, allowing more flexibility in creating complex objects. A service is a constructor function that is instantiated using the `new` keyword. The choice often depends on personal preference and the complexity of the component.

12. What are filters in AngularJS and how are they used?

    • Answer: Filters format or modify data before it's displayed in the view. They are applied to expressions within the template using the pipe symbol (`|`). Common built-in filters include `date`, `currency`, `lowercase`, `uppercase`, `number`, and `orderBy`. Custom filters can also be created.

13. How do you test AngularJS applications?

    • Answer: AngularJS applications are tested using various approaches, including unit testing (testing individual components) and end-to-end testing (testing the entire application flow). Tools like Karma and Jasmine are commonly used for unit testing, and Protractor is often used for end-to-end testing. Dependency injection facilitates testing by allowing components to be easily mocked and isolated.

14. Explain the digest cycle in AngularJS.

    • Answer: The digest cycle is AngularJS's mechanism for detecting changes in the model and updating the view accordingly. It repeatedly checks for changes in scope variables and updates the view when changes are detected. This happens automatically, but developers can also trigger a digest cycle manually using `$scope.$apply()` or `$scope.$digest()`.

15. What are some common performance optimization techniques for AngularJS applications?

    • Answer: Performance optimization techniques include minimizing DOM manipulation, using `ng-if` instead of `ng-show` where appropriate, using one-time bindings (`::`), limiting the use of watches, using efficient data structures, and optimizing HTTP requests. Proper use of directives and avoiding unnecessary digest cycles are also critical.

16. How do you handle errors in AngularJS?

    • Answer: Error handling in AngularJS typically involves using `try...catch` blocks within controllers and services. For HTTP requests, the `catch()` method of the promise returned by `$http` is used to handle errors. Custom error handling services can be created to centralize error management and logging.

17. What are some best practices for building maintainable AngularJS applications?

    • Answer: Best practices include adhering to the MVC pattern, using dependency injection effectively, writing clean and well-documented code, utilizing a consistent coding style, breaking down the application into smaller, reusable components, writing comprehensive tests, and leveraging a version control system.

18. Explain the difference between AngularJS and Angular (Angular 2+).

    • Answer: AngularJS (Angular 1.x) and Angular (Angular 2+) are significantly different. AngularJS is based on JavaScript, while Angular uses TypeScript. Angular has a component-based architecture, while AngularJS uses directives and controllers. Angular is faster and more scalable. AngularJS is less performant and can be harder to maintain for large applications.

19. Describe your experience working with AngularJS in a team environment.

    • Answer: (This requires a personalized answer based on your experience. Describe your roles, collaborations, conflict resolution, and use of version control and code review processes.)

20. How have you kept your AngularJS skills up-to-date over the years?

    • Answer: (This requires a personalized answer describing your learning methods. Mention online courses, conferences, books, blogs, personal projects, etc.)

21. Describe a challenging AngularJS project you worked on and how you overcame the challenges.

    • Answer: (This requires a personalized answer detailing a specific project, its challenges, and the solutions you implemented. Focus on problem-solving skills and technical proficiency.)

22. What are your preferred tools and technologies for AngularJS development?

    • Answer: (List your preferred IDE, testing frameworks, build tools, etc.)

23. What are some common security vulnerabilities in AngularJS applications and how can they be mitigated?

    • Answer: (Discuss XSS, CSRF, and other vulnerabilities and how to prevent them using techniques like input sanitization, using HTTPS, and proper authentication and authorization.)

24. Explain your understanding of the AngularJS lifecycle.

    • Answer: (Detail the phases: compilation, linking, and digest cycle.)

25. How do you handle internationalization (i18n) in AngularJS?

    • Answer: (Discuss techniques for handling different languages and locales.)

26. How would you optimize an AngularJS application for mobile devices?

    • Answer: (Discuss techniques like lazy loading, efficient data fetching, and optimization for touch events.)

27. How familiar are you with different testing methodologies (unit, integration, end-to-end)?

    • Answer: (Detail your familiarity and experience with each type.)

28. Describe your experience with different build tools for AngularJS projects (e.g., Grunt, Gulp, Webpack).

    • Answer: (Detail your experience with any of these tools.)

29. How do you approach debugging AngularJS applications?

    • Answer: (Discuss using browser developer tools, logging, and debugging techniques.)

30. What are some common design patterns used in AngularJS development?

    • Answer: (Mention MVC, Factory, Service, Singleton, Observer, etc.)

31. How do you handle versioning and dependency management in AngularJS projects?

    • Answer: (Discuss using Bower, npm, or yarn.)

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