Angular.js Interview Questions and Answers for 2 years experience

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AngularJS Interview Questions and Answers

  1. What is AngularJS?

    • Answer: AngularJS is a structural framework for dynamic web apps. It lets you use HTML as your template language and extends HTML's syntax to express your application's components clearly and succinctly. It's 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.

  2. Explain the concept of MVC in AngularJS.

    • Answer: AngularJS follows the Model-View-Controller (MVC) architectural pattern. The Model represents the data, the View displays the data, and the Controller acts as an intermediary, handling user interactions and updating the Model and View accordingly. While AngularJS doesn't strictly adhere to a pure MVC, it embodies its principles effectively.

  3. What are directives in AngularJS? Give examples.

    • Answer: Directives extend HTML with custom attributes, elements, and CSS classes. They let you create reusable components. Examples include `ng-model`, `ng-repeat`, `ng-if`, `ng-bind`, and custom directives you create to encapsulate specific functionality.

  4. Explain data binding in AngularJS. What are its types?

    • Answer: Data binding is the automatic synchronization of data between the model and the view. AngularJS offers two-way data binding, where changes in the model automatically update the view, and vice-versa. One-way data binding is also possible, updating only in one direction.

  5. What is the role of scope in AngularJS?

    • Answer: Scope is the object that acts as a glue between the controller and the view. It's a JavaScript object that holds application data and methods accessible within the view using expressions. It facilitates data binding and allows controllers to interact with the view.

  6. What are services in AngularJS? How are they created?

    • Answer: Services are singleton objects that provide specific functionality to controllers and other parts of the application. They promote code reusability and maintainability. They are created using the `service`, `factory`, or `provider` methods.

  7. Explain dependency injection in AngularJS.

    • Answer: Dependency injection is a design pattern where dependencies are provided to a component rather than being created by it. AngularJS uses dependency injection to manage the creation and configuration of objects, promoting modularity and testability.

  8. What are filters in AngularJS? Give examples.

    • Answer: Filters format data for display in the view. Examples include `currency`, `date`, `uppercase`, `lowercase`, `limitTo`, and custom filters you can create to process data in specific ways.

  9. How do you handle routing in AngularJS?

    • Answer: AngularJS uses the `ngRoute` module (or other routing libraries) to handle routing. It allows you to define different views and controllers associated with specific URLs, creating a single-page application with multiple views.

  10. What are expressions in AngularJS?

    • Answer: Expressions are JavaScript code snippets that are evaluated within AngularJS's context. They are used to display data, bind data to the view, and perform calculations within the template.

  11. Explain the difference between `ng-repeat` and `ng-for` (if applicable to your experience).

    • Answer: `ng-repeat` is the AngularJS way to iterate over collections. `ng-for` is its equivalent in Angular (version 2 and above). While similar in function, `ng-for` offers improvements in performance and features compared to `ng-repeat`.

  12. How do you handle events in AngularJS?

    • Answer: Events are handled using directives like `ng-click`, `ng-submit`, `ng-change`, and other event-handling directives. These directives bind specific events to functions in the controller.

  13. What are promises in AngularJS?

    • Answer: Promises represent the eventual result of an asynchronous operation. They help handle asynchronous tasks like AJAX calls more cleanly and prevent callback hell.

  14. Explain $http service in AngularJS.

    • Answer: The `$http` service is used to make AJAX requests to communicate with servers. It simplifies the process of making HTTP requests (GET, POST, PUT, DELETE etc.).

  15. How do you test AngularJS applications?

    • Answer: AngularJS applications are tested using various approaches, including unit testing (using frameworks like Jasmine and Karma) and end-to-end testing (using Protractor).

  16. What are some best practices for AngularJS development?

    • Answer: Best practices include using dependency injection effectively, keeping controllers lean and focused, using services for reusable logic, following a consistent coding style, and writing thorough unit tests.

  17. Explain how to create a custom directive in AngularJS.

    • Answer: Custom directives are created by defining a function that takes a factory function as a parameter. This factory function returns an object which defines various aspects of the directive, such as its behavior (restrict, template, controller, link functions, etc.).

  18. How do you handle errors in AngularJS?

    • Answer: Errors can be handled using `try...catch` blocks in controllers or by using promise error handling mechanisms for asynchronous operations. $http requests also provide ways to intercept and handle errors.

  19. Describe your experience with AngularJS performance optimization.

    • Answer: (This answer should be tailored to your experience, but could include: minimizing watchers, using one-way data binding where appropriate, optimizing `ng-repeat`, using caching mechanisms, minimizing DOM manipulation, and profiling the application for performance bottlenecks.)

  20. How would you debug an AngularJS application?

    • Answer: Debugging can be done using the browser's developer tools (console, debugger), using logging statements, and by utilizing AngularJS's debugging tools if available. Using a good IDE with debugging support is also crucial.

  21. What are some common challenges you faced while working with AngularJS and how did you overcome them?

    • Answer: (This requires a personalized answer based on your actual experiences, but examples could include: dealing with scope inheritance issues, managing complex data structures, handling asynchronous operations, optimizing performance, or resolving conflicts with other libraries.)

  22. Explain the concept of digest cycle in AngularJS.

    • Answer: The digest cycle is the process by which AngularJS checks for changes in the model and updates the view accordingly. It iteratively compares the current state of the model with its previous state, detecting any changes and applying them to the view.

  23. What is the difference between a factory and a service in AngularJS?

    • Answer: Both factories and services are ways to create services in AngularJS. A factory is a function that returns an object, giving you more flexibility in constructing the service object. A service is a constructor function that AngularJS instantiates. The choice depends on the specific needs of the service.

  24. How do you handle authentication and authorization in an AngularJS application?

    • Answer: Authentication and authorization often involve using services to interact with a backend API for user login and verification. This typically involves storing authentication tokens (like JWTs) securely and using those tokens to protect routes and data access within the application.

  25. Explain your experience with different AngularJS modules.

    • Answer: (This answer should list the modules you have worked with, like ngRoute, ngResource, ngSanitize, etc., and describe your experience with each.)

  26. How would you improve the SEO of an AngularJS application?

    • Answer: AngularJS applications can sometimes be challenging for SEO because of the dynamic nature of the content. Techniques to improve SEO include using server-side rendering (SSR) or using techniques to make the application crawlable by search engines (e.g., pre-rendering).

  27. What are the limitations of AngularJS?

    • Answer: AngularJS can become complex for very large applications. Its digest cycle can impact performance under certain circumstances, and the lack of built-in support for newer features found in Angular (version 2 and above) leads many developers to migrate to the newer framework.

  28. What are some alternatives to AngularJS?

    • Answer: Alternatives include Angular (version 2 and above), React, Vue.js, and other modern JavaScript frameworks.

  29. Explain your understanding of the two-way data binding process in AngularJS.

    • Answer: Two-way data binding means that changes in the model automatically reflect in the view, and vice versa. This is achieved through AngularJS's digest cycle and the use of watchers, which constantly monitor the model for changes.

  30. How would you structure a large AngularJS application?

    • Answer: A large application should be structured using modules to break down the application into smaller, manageable pieces. This promotes reusability and maintainability. Following a clear folder structure and using a consistent coding style are also crucial.

  31. Describe your experience working with RESTful APIs in AngularJS.

    • Answer: (Describe your experience with making API calls using the $http service, handling responses, error handling, and any other relevant aspects.)

  32. How do you handle asynchronous operations in AngularJS?

    • Answer: Asynchronous operations are typically handled using promises (as returned by $http service) or callbacks. Using promises leads to cleaner and more maintainable code compared to nested callbacks.

  33. What is the purpose of the `$scope.$apply()` method?

    • Answer: `$scope.$apply()` is used to trigger a digest cycle manually. This is needed when changes to the model occur outside the context of AngularJS, such as in asynchronous callbacks.

  34. How do you manage state in an AngularJS application?

    • Answer: State can be managed using services, factories, or local storage. For more complex applications, using a dedicated state management solution might be needed.

  35. Explain your experience with unit testing AngularJS controllers.

    • Answer: (Explain your experience with testing controllers using frameworks like Jasmine and Karma, and describe your approach to testing different aspects of the controller's logic.)

  36. How do you handle form validation in AngularJS?

    • Answer: Form validation can be handled using AngularJS's built-in validation directives (like `ng-required`, `ng-pattern`, etc.) and by adding custom validation logic using controllers or directives.

  37. What are the advantages of using directives over plain JavaScript?

    • Answer: Directives promote code reusability, encapsulation, and maintainability. They allow you to create custom HTML elements or attributes that encapsulate specific functionality.

  38. How do you optimize the performance of a large AngularJS application? Provide specific examples.

    • Answer: Optimizing performance involves various techniques like: minimizing watchers (using one-way binding where possible), efficiently using `ng-repeat` (potentially with track by), limiting DOM manipulation, using caching, and profiling the application to identify performance bottlenecks.

  39. Explain your understanding of AngularJS's dependency injection system. How does it work?

    • Answer: AngularJS uses dependency injection to provide dependencies to components (controllers, services, etc.). When a component is created, AngularJS injects the required dependencies based on the function's arguments. This improves modularity and testability.

  40. Describe a complex AngularJS project you worked on and the challenges you faced.

    • Answer: (This requires a detailed, personalized answer describing a past project, the challenges encountered, and how you resolved them. Be specific and highlight your problem-solving skills.)

  41. How do you approach debugging memory leaks in AngularJS?

    • Answer: Identifying memory leaks involves using browser developer tools to monitor memory usage, identifying potentially problematic patterns (like unintentional scope inheritance or event listeners that aren't properly removed), and testing different approaches to resolve issues.

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