Top 50 AngularJS Interview Questions

AngularJS, an open-source JavaScript framework maintained by Google, has been widely adopted for building dynamic web applications. Its powerful features, including two-way data binding, dependency injection, and directives, make it an essential tool for modern web development. If you’re preparing for an AngularJS interview, this article lists the top 50 AngularJS interview questions, categorized for beginners, intermediate, and advanced developers.

Beginner-Level AngularJS Interview Questions

1. What is AngularJS?

AngularJS is an open-source front-end web application framework designed to simplify the development and testing of dynamic web applications. It extends HTML with additional attributes and provides a two-way data-binding mechanism.

2. What are the main features of AngularJS?

• Two-way data binding
• MVC (Model-View-Controller) architecture
• Dependency injection
• Directives
• Filters
• Templates

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

Two-way data binding synchronizes the data between the model and the view. Changes in the model automatically update the view and vice versa.

4. What are directives in AngularJS?

Directives are special markers on elements in the DOM that tell AngularJS to do something (e.g., modify elements, bind data). Examples include ng-model, ng-bind, and ng-app.

5. What is the role of the $scope object in AngularJS?

The $scope object is a bridge between the HTML view and the JavaScript controller. It holds the data and methods that the view can access.

6. What is an AngularJS module?

A module is a container for different parts of an application, such as controllers, services, directives, filters, and configuration information.

7. What is the purpose of the ng-app directive?

The ng-app directive initializes an AngularJS application.

8. What is a controller in AngularJS?

A controller in AngularJS is a JavaScript function that manages the application’s data and behavior.

9. What is dependency injection in AngularJS?

Dependency injection is a design pattern used to provide dependencies to components like services, directives, or controllers in AngularJS.

10. What are filters in AngularJS?

Filters format data displayed in the view. Common filters include currency, uppercase, lowercase, and filter.

Intermediate-Level AngularJS Interview Questions

11. What are services in AngularJS?

Services are reusable singleton objects that encapsulate common functionalities like logging, data fetching, and calculations.

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

Custom directives are created using the directive method in a module. Example:

13. What is $watch in AngularJS?

The $watch function monitors changes in scope variables and executes a callback when the value changes.

14. What is $digest in AngularJS?

The $digest cycle is a process where AngularJS checks all watched variables to update the DOM if any changes occur.

15. What is the difference between $digest and $apply?

• $digest: Updates the scope of the current context.
• $apply: Executes an expression and triggers a $digest cycle.

16. What is the purpose of $http in AngularJS?

The $http service is used to make AJAX requests to fetch or send data to a server.

17. What are the different types of directives in AngularJS?

• Element directives (e.g., <my-directive></my-directive>)
• Attribute directives (e.g., <div my-directive></div>)
• CSS class directives (e.g., <div class="my-directive"></div>)
• Comment directives (e.g., <!-- directive: my-directive -->)

18. What is the $timeout service?

The $timeout service is AngularJS’s wrapper for the setTimeout function.

19. How do you handle events in AngularJS?

AngularJS provides directives like ng-click, ng-submit, and ng-change for event handling.

20. What is the difference between ng-repeat and ng-options?

• ng-repeat is used to iterate over a collection and create DOM elements dynamically.
• ng-options is used to populate a <select> dropdown with options.

Advanced-Level AngularJS Interview Questions

21. What is $q in AngularJS?

The $q service is AngularJS’s implementation of promises, which handle asynchronous operations.

22. What is $rootScope in AngularJS?

The $rootScope is the parent scope of all other scopes in an AngularJS application.

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

• Factory: Returns an object created inside the factory function.
• Service: Returns an instance of a function.
• Provider: Configurable during the application’s configuration phase.

24. What is the difference between compile and link in directives?

• Compile: Transforms the template before it is linked.
• Link: Establishes the connection between the DOM and the scope.

25. How does AngularJS handle exceptions?

AngularJS provides the $exceptionHandler service to handle exceptions and log errors.

26. What is the purpose of $location in AngularJS?

The $location service allows you to read or change the URL in the browser.

27. What are AngularJS expressions?

AngularJS expressions bind data to the HTML. They are written inside double curly braces {{ }}.

28. What is $scope.$on() used for?

The $scope.$on() method listens for events broadcasted or emitted within an AngularJS application.

29. What is $broadcast in AngularJS?

The $broadcast method sends an event downwards to all child scopes.

30. What is $emit in AngularJS?

The $emit method sends an event upwards to all parent scopes.

Common AngularJS Coding Questions

31. Write a simple example of two-way data binding.

32. How do you create a module in AngularJS?

33. Write a simple custom filter.

34. How do you handle form validation in AngularJS?

AngularJS provides built-in validation directives like ng-required, ng-minlength, and ng-pattern.

35. Explain how $apply() works in AngularJS.

The $apply() function executes a given expression and triggers the $digest cycle.

Other Advanced Questions

36. What is the $interpolate service?
37. How do you optimize performance in AngularJS?
38. What are one-time bindings?
39. How do you set up routing in AngularJS using ngRoute?
40. What is $cacheFactory?
41. What is lazy loading in AngularJS?
42. How do you debug AngularJS applications?
43. How is $templateCache used in AngularJS?
44. What is the difference between $scope and controllerAs syntax?
45. How does AngularJS handle XSS (Cross-Site Scripting)?
46. What is $resource?
47. Explain the role of $parse.
48. How do you create nested controllers in AngularJS?
49. What is $compile in AngularJS?
50. What are AngularJS decorators?

AngularJS continues to be an essential framework for web developers, despite the rise of Angular. Mastering these top 50 AngularJS interview questions can significantly improve your chances of acing your interview and landing your next job.