AngularJS Interview Questions

Fundamentals

1. What is AngularJS?

Ans: AngularJS is a powerful JavaScript framework developed by Google. It’s used to build dynamic and interactive web applications by extending HTML with new attributes called directives.

2. What are the key features of AngularJS?

Ans:

• Data Binding: Automatic synchronization between the model and the view.
• Directives: Extend HTML vocabulary with custom attributes.
• Dependency Injection: Manages component dependencies effectively.
• MVC Architecture: Promotes a clean separation of concerns.
• Templating: Allows for creating reusable HTML templates.
• Testing: Provides built-in features for easy unit and end-to-end testing.

3. Explain the concept of two-way data binding in AngularJS.

Ans: Two-way data binding automatically synchronizes data between the model (JavaScript objects) and the view (HTML). Any changes made to the model are instantly reflected in the view, and vice versa.

4. What are directives in AngularJS?

Ans: Directives are markers on DOM elements (such as elements, attributes, CSS classes, and comments) that tell AngularJS to do something special with that element. They extend HTML’s syntax.

5. List some common built-in directives in AngularJS.

Ans:

• ng-app: Defines the root of an AngularJS application.
• ng-model: Binds data to input elements.
• ng-bind: Binds data to HTML elements.
• ng-click: Adds event listeners to elements.
• ng-repeat: Iterates over collections of data.
• ng-if: Conditionally displays elements.
• ng-show/ng-hide: Controls the visibility of elements.

Architecture & Concepts

6. Explain the MVC architecture in AngularJS.

Ans:

• Model: Represents the data of the application.
• View: Displays the data to the user.
• Controller: Handles user interactions and updates the model.

7. What is a scope in AngularJS?

Ans: Scope is an object that holds the application data and provides a way to share data between controllers and views.

8. How does dependency injection work in AngularJS?

Ans: AngularJS can automatically inject the dependencies of a component (like services) into that component, making it easier to test and maintain.

9. What are services in AngularJS?

Ans: Services are singleton objects that can be shared across different parts of the application. They are used to perform tasks like data access, logging, and communication with external APIs.

10. What are filters in AngularJS?

Ans: Filters are used to format data before it is displayed in the view. For example, you can use filters to format dates, currency, and numbers.

Directives & Templating

11. How do you create a custom directive in AngularJS?

Ans: You create a custom directive by registering it with the module.directive() method. This method takes the directive name and a directive definition function as arguments.

12. Explain the different types of directives.

Ans:

• Element directives: Define new HTML elements.
• Attribute directives: Modify the behavior of existing elements.
• Class directives: Add or remove CSS classes from elements.
• Comment directives: Execute code within a comment.

13. How do you use ng-repeat to iterate over an array?

Ans:

<ul>
  <li ng-repeat="item in items">{{ item }}</li>
</ul>

14. How do you use ng-if to conditionally display elements?

Ans:

<div ng-if="condition">This element will be displayed if 'condition' is true.</div>

15. How do you create reusable templates in AngularJS?

Ans: You can create reusable templates using the <script type="text/ng-template"> tag.

Data Binding & Expressions

16. What are expressions in AngularJS?

Ans: Expressions are JavaScript-like code snippets that are evaluated within the view. They are used to bind data to the view and perform calculations.

17. Explain how to bind data to input fields.

Ans: Use the ng-model directive to bind data to input fields.

18. How do you handle events in AngularJS?

Ans: Use event handlers like ng-click, ng-submit, and ng-change to handle user interactions.

19. What are the different ways to bind data to the view?

Ans:

• ng-bind: Binds data to HTML elements.
• {{ expression }}: Interpolates data within the view.
• ng-model: Binds data to input elements.

Routing & Navigation

20. What is the role of $routeProvider in AngularJS?

Ans: $routeProvider is used to configure the application’s routes. It defines how the application should respond to different URL paths.

21. How do you define routes in AngularJS?

Ans:

$routeProvider
  .when('/path1', { 
    templateUrl: 'path1.html', 
    controller: 'Path1Ctrl' 
  })
  .when('/path2', { 
    templateUrl: 'path2.html', 
    controller: 'Path2Ctrl' 
  })
  .otherwise({ redirectTo: '/path1' }); 

22. How do you handle navigation in AngularJS?

Ans:

• Use the $location service to get or set the current URL.
• Use the $routeParams service to access route parameters.

Testing

23. Why is testing important in AngularJS applications?

Ans: Testing ensures the quality and stability of the application. It helps to identify and fix bugs early in the development process.

24. What are the different types of testing in AngularJS?

Ans:

• Unit tests: Test individual components in isolation.
• End-to-end tests: Test the entire application from the user’s perspective.

25. How do you write unit tests for AngularJS components?

Ans: Use testing frameworks like Jasmine or Mocha to write unit tests. AngularJS provides built-in tools to make testing easier.

Advanced Topics

26. What is a factory in AngularJS?

Ans: A factory is a function that returns an object or a value. It’s a common way to create services in AngularJS.

27. What is a service in AngularJS?

Ans: A service is a singleton object that can be shared across different parts of the application. They are used to perform tasks like data access, logging, and communication with external APIs.

28. What is a provider in AngularJS?

Ans: A provider is a function that returns a service. It gives you more control over how the service is created.

29. What is the difference between a factory and a service?

Ans: Factories return an object or a value, while services are constructors.

30. What is the difference between a service and a provider?

Ans: Providers give you more control over how the service is created, while services are the actual objects that are injected into components.

31. What is the role of $http service in AngularJS?

Ans: The $http service is used to make HTTP requests (e.g., GET, POST, PUT, DELETE) to interact with external APIs or servers.

32. How do you handle asynchronous operations in AngularJS?

Ans: Use promises or the $q service to handle asynchronous operations like HTTP requests and timeouts.

33. What is the purpose of $rootScope in AngularJS?

Ans: $rootScope is the parent scope of all other scopes in the application. It’s used to broadcast events and share data across the entire application.

34. What are animations in AngularJS?

Ans: AngularJS provides built-in support for creating animations using CSS transitions and keyframes.

35. How do you implement forms in AngularJS?

Ans: Use the ng-model directive to bind data to form inputs and the ng-submit directive to handle form submissions.

36. How do you handle form validation in AngularJS?

Ans: Use built-in form validation directives like required, minlength, and maxlength, or create custom validation directives.

37. What are filters in AngularJS?

Ans: Filters are used to format data before it is displayed in the view. For example, you can use filters to format dates, currency, and numbers.

38. How do you create a custom filter in AngularJS?

Ans: Create a custom filter by registering it with the module.filter() method.

39. What is the difference between ng-show and ng-if directives?

Ans:

• ng-show: Hides or shows the element by changing its CSS display property.
• ng-if: Removes or adds the element from the DOM based on the condition.

40. What is the purpose of $watch in AngularJS?

Ans: $watch is used to observe changes to a model or an expression and execute a function when the value changes.

Performance & Best Practices

41. How can you improve the performance of an AngularJS application?

Ans:

• Minimize the number of watches.
• Use ng-if instead of ng-show when possible.
• Optimize digest cycles.
• Minimize the number of DOM manipulations.
• Use caching strategies.

42. What are some best practices for writing clean and maintainable AngularJS code?

Ans:

• Follow the MVC architecture.
• Use dependency injection effectively.
• Write unit tests for your components.
• Keep your components small and reusable.
• Use a consistent coding style.

43. How do you debug AngularJS applications?

Ans: Use the browser’s developer tools to debug AngularJS applications. You can inspect the scope, view, and controller in the browser console.

44. What are some common security vulnerabilities in AngularJS applications?

Ans:

• Cross-Site Scripting (XSS)
• Cross-Site Request Forgery (CSRF)
• Injection attacks

45. How can you prevent security vulnerabilities in AngularJS applications?

Ans:

• Sanitize user input.
• Use HTTPS.
• Implement proper authentication and authorization.
• Keep your AngularJS version updated.

Integration & Migration

46. How can you integrate AngularJS with other frameworks or libraries?

Ans: AngularJS can be integrated with other JavaScript libraries and frameworks like jQuery, Bootstrap, and D3.js.

47. What are some considerations when migrating from AngularJS to a newer framework like Angular?

Ans:

• Component structure: The component structures in AngularJS and Angular are different.
• Data binding: Angular uses a different approach to data binding.
• Routing: The routing mechanisms are different.
• Testing: The testing strategies may need to be adjusted.

48. How can you gradually migrate an AngularJS application to a newer framework?

Ans:

• Start by creating new components using the newer framework.
• Gradually replace existing AngularJS components with the new ones.
• Use a hybrid approach where you combine both frameworks in the same application.

49. What are the advantages of migrating from AngularJS to a newer framework?

Ans:

• Improved performance
• Better developer experience
• Access to newer features and APIs
• Improved maintainability and scalability

50. What are the future prospects of AngularJS?

Ans: While AngularJS is still actively maintained, the focus has shifted to newer versions of Angular. It’s recommended to consider migrating to a newer version for better long-term support and access to the latest features.