AngularJS Interview Questions

Top 50 AngularJS Interview Questions & Answers: Land Your Dream Job

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:

HTML

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

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

Ans:

HTML

<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 ng-include directive. It loads HTML fragments from external files and embeds them into the view.

html
<div ng-include="'template.html'"></div>

Routing & Navigation

16. What is routing in AngularJS?

Ans: Routing is the mechanism that allows navigation between different views or pages in a single-page application (SPA) without reloading the entire page.

17. How is routing implemented in AngularJS?

Ans: AngularJS uses the ngRoute module. You configure routes using $routeProvider.

javascript

app.config(function($routeProvider) {
$routeProvider
.when('/home', { templateUrl: 'home.html', controller: 'HomeCtrl' })
.when('/about', { templateUrl: 'about.html', controller: 'AboutCtrl' })
.otherwise({ redirectTo: '/home' });
});

18. What is $routeProvider?

Ans: $routeProvider is a service used to configure routes in AngularJS applications using the ngRoute module.

19. What is $location in AngularJS?

Ans: $location service parses the URL in the browser address bar and allows you to manipulate it.

20. What is $routeParams?

Ans: $routeParams is used to retrieve parameters passed in the route URL.

Controllers & Scope

21. How do you define a controller in AngularJS?

Ans: A controller is defined using the .controller() method on an AngularJS module.

javascript

app.controller('MyController', function($scope) {
$scope.message = 'Hello, AngularJS!';
});

22. What is the role of a controller in AngularJS?

Ans: Controllers act as a link between the view and the model. They initialize data and define functions that the view can use.

23. Can controllers be nested in AngularJS?

Ans: Yes, AngularJS supports nested controllers. Child controllers can access data from parent scopes.

24. What is $scope.$watch()?

Ans: It allows you to monitor changes in a model value and execute a callback when that value changes.

Events & Expressions

25. What are AngularJS expressions?

Ans: Expressions are code snippets within double curly braces {{ }} used to bind data to HTML.

26. Difference between AngularJS expressions and JavaScript expressions?

Ans:

  • AngularJS expressions don’t support conditionals like if, loops, or new.
  • They are evaluated against the scope object, not the global window.

27. How do you handle events in AngularJS?

Ans: Using event directives like ng-click, ng-dblclick, ng-change, etc.

Performance & Optimization

28. How to improve performance in AngularJS applications?

Ans: Use track by in ng-repeat

  • Avoid unnecessary $watch

  • Use one-time binding ::

  • Use ng-if instead of ng-show for conditional rendering

29. What is one-time binding?

Ans: One-time binding ({{::expression}}) binds data once and does not watch for changes, improving performance.

Services & Factories

30. Difference between service and factory in AngularJS?

Ans:

  • Service returns a singleton object (uses this)

  • Factory returns the value returned by the function (customizable)

31. How to create a service in AngularJS?

Ans: javascript

app.service('MyService', function() {
this.sayHello = function() {
return "Hello";
};
});

32. How to create a factory in AngularJS?

Ans: javascript

app.factory('MyFactory', function() {
return {
sayHello: function() {
return "Hello";
}
};
});

Dependency Injection & Testing

33. What is dependency injection in AngularJS?

Ans: It is a design pattern where components are given their dependencies rather than hardcoding them inside.

34. How is testing supported in AngularJS?

Ans: AngularJS supports both unit and end-to-end testing using tools like Jasmine and Karma.

Form Handling & Validation

35. How does form validation work in AngularJS?

Ans: AngularJS uses built-in directives like required, ng-minlength, ng-pattern for client-side validation. It also provides classes like ng-valid, ng-invalid for styling.

36. What is $valid, $dirty, and $touched in forms?

Ans:

  • $valid: True if the input is valid
  • $dirty: True if the value has been changed

  • $touched: True if the input has been focused and left

Advanced Topics

37. What is $digest cycle?

Ans: It is the process in which AngularJS checks for changes in the model and updates the DOM accordingly.

38. What is $apply()?

Ans: $apply() is used to manually trigger the digest cycle to detect changes outside AngularJS (like setTimeout or jQuery).

39. What is $emit, $broadcast, and $on in AngularJS?

Ans:

  • $emit: Sends event upward to parent scopes
  • $broadcast: Sends event downward to child scopes

  • $on: Listens for events

40. What is a $q service in AngularJS?

Ans: $q is a service that helps run functions asynchronously and allows you to register callbacks using promises.

Miscellaneous

41. What is $http in AngularJS?

Ans: $http is a service used to make AJAX requests to the server.

42. What is $timeout and $interval?

Ans: AngularJS wrappers for setTimeout and setInterval, integrated with the digest cycle.

43. What is $rootScope?

Ans: $rootScope is the top-most scope that all other scopes inherit from.

44. What is $compile service?

Ans: $compile compiles HTML strings into a template function, which binds data to the DOM.

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

Ans:

  • Compile: Modifies the template DOM before it is rendered

  • Link: Binds the compiled template with scope and adds behavior

Debugging & Tools

46. How to debug AngularJS applications?

Ans:

  • Use browser dev tools
  • Use console.log() in controllers/services

  • AngularJS Batarang (Chrome extension)

47. What are some commonly used AngularJS development tools?

Ans:

  • Batarang
  • Karma
  • Protractor

  • Jasmine

Versioning & Transition

48. What is the difference between AngularJS and Angular?

Ans:

  • AngularJS (1.x) is based on JavaScript
  • Angular (2+) is based on TypeScript

  • Angular has better performance, modularity, and mobile support

49. Is AngularJS still used in 2025?

Ans: It’s largely outdated and replaced by Angular and other modern frameworks, but some legacy systems still use it.

50. How do you migrate from AngularJS to Angular?

Ans: Use the Angular Upgrade module (@angular/upgrade) to run AngularJS and Angular together and gradually migrate components.

Popular Courses

Oracle ATG Training

ATG Training

Saviynt Training

Saviynt Training

Leave a Comment