100 AngularJS interview questions along with their short answers

Here are 100 AngularJS interview questions along with their short answers:

Basics:

1. What is AngularJS?

• AngularJS is a JavaScript framework developed by Google for building dynamic web applications.

1. What are the key features of AngularJS?

• Key features include two-way data binding, dependency injection, directives, and a modular structure.

1. Explain two-way data binding in AngularJS.

• Two-way data binding allows automatic synchronization of data between the model and the view, ensuring that changes in one are reflected in the other.

1. What is dependency injection in AngularJS?

• Dependency injection is a design pattern that allows you to inject dependencies (services or objects) into components.

1. What is an AngularJS directive?

• A directive is a marker in the DOM that tells AngularJS to attach a specific behavior to an HTML element.

1. What is the role of controllers in AngularJS?

• Controllers are responsible for managing the data and behavior of a view in AngularJS.

1. What is the AngularJS module?

• A module is a container for different parts of an AngularJS application, such as controllers, services, and directives.

1. Explain the AngularJS digest cycle.

• The digest cycle is the process by which AngularJS keeps data synchronized between the model and the view.

1. What is AngularJS’s ng-app directive used for?

• The ng-app directive defines the root element of an AngularJS application and initializes it.

1. What is a template in AngularJS?
   • A template is an HTML file or string that defines the structure of a view in an AngularJS application.

Directives:

11. What is the ng-model directive used for?
    • The ng-model directive is used for two-way data binding, linking an input element’s value to a model property.
12. Explain the ng-repeat directive in AngularJS.
    • The ng-repeat directive is used for iterating over a collection and rendering elements for each item.
13. What is the purpose of the ng-if directive?
    • The ng-if directive conditionally renders or removes an element from the DOM based on an expression.
14. What is the ng-show and ng-hide directive used for?
    • ng-show and ng-hide directives conditionally display or hide elements based on an expression.
15. Explain the ng-click directive.
    • The ng-click directive is used to define a function to be executed when an element is clicked.
16. What is the ng-src directive used for?
    • The ng-src directive binds the src attribute of an HTML element to an expression, typically used for images.
17. What is the purpose of the ng-class directive in AngularJS?
    • The ng-class directive dynamically applies CSS classes to elements based on expression evaluation.
18. What is the ng-style directive used for?
    • The ng-style directive allows you to dynamically set CSS styles on an element based on an expression.
19. Explain the ng-switch directive in AngularJS.
    • The ng-switch directive is used for conditionally rendering content based on a provided value.
20. What is the ng-include directive used for?
    • The ng-include directive is used to include an external HTML file into the current template.

Controllers:

21. How do you define a controller in AngularJS?
    • A controller is defined using the controller method and attached to a module.
22. What is the purpose of the $scope object in AngularJS controllers?
    • The $scope object is a bridge between the controller and the view, allowing data and functions to be accessible in the template.
23. How do you share data between controllers in AngularJS?
    • You can share data between controllers using services or the $rootScope object.
24. What is a controller alias in AngularJS?
    • A controller alias is used to avoid naming conflicts when multiple controllers are used within the same scope.
25. Explain the concept of controller inheritance in AngularJS.
    • Child controllers inherit properties and methods from their parent controllers, allowing for a hierarchy of controllers.
26. What is a controller constructor function in AngularJS?
    • A controller constructor function is used to define a controller and is invoked when the controller is instantiated.
27. What is the difference between the $scope object and the this keyword in a controller?
    • $scope is used for data binding between the controller and the view, while this is used for defining functions and properties directly on the controller.
28. How do you handle controller initialization in AngularJS?
    • Controller initialization can be handled by using the controllerAs syntax or the
    ng-controller directive.
29. What is the role of the $inject property in AngularJS controllers?
    • The $inject property is used to declare and specify dependencies for a controller when minification renames function parameters.
30. What is a route parameter in AngularJS?
    • Route parameters allow dynamic values to be passed in the URL and accessed by the controller.

Services and Factories:

31. What is an AngularJS service?
    • A service is a singleton object that provides methods and data that can be shared across multiple parts of an application.
32. How do you create a custom service in AngularJS?
    • A custom service is created using the service or factory method and registered with a module.
33. What is the difference between an AngularJS service and factory?
    • A service is a constructor function, while a factory is a function that returns an object or value.
34. What is the purpose of the $http service in AngularJS?
    • The $http service is used for making HTTP requests and interacting with RESTful APIs.
35. Explain the $resource service in AngularJS.
    • $resource is a higher-level service for working with RESTful APIs and simplifying CRUD operations.
36. What is the purpose of the $q service in AngularJS?
    • The $q service provides a promise-based interface for handling asynchronous operations.
37. What is the AngularJS $location service used for?
    • The $location service allows you to work with the browser’s URL, navigate to different routes, and access URL parameters.
38. What is the $rootScope object in AngularJS?
    • The $rootScope object is the parent scope for all scopes in an AngularJS application and can be used to share data across controllers.
39. Explain the $timeout and $interval services in AngularJS.
    • $timeout is used to delay the execution of a function, and $interval is used for repeatedly running a function at specified intervals.
40. What is a provider in AngularJS, and how is it used to configure services?
    • A provider is used to configure services before they are injected into controllers, directives, or other services.

Dependency Injection:

41. What is dependency injection (DI) in AngularJS?
    • Dependency injection is a design pattern that enables the injection of dependencies into a component rather than hard-coding them.
42. How does AngularJS implement dependency injection?
    • AngularJS uses the $injector to manage and inject dependencies into controllers, services, and other components.
43. Explain the concept of implicit and explicit annotation in AngularJS dependency injection.
    • Implicit annotation relies on the order of parameters to match dependencies, while explicit annotation uses an array to specify dependencies.
44. What is a service dependency in AngularJS?
    • A service dependency is a dependency on a reusable service that can be injected into controllers, directives, or other services.
45. What are constant dependencies in AngularJS?
    • Constant dependencies are values that can be injected into components and are typically used for configuration settings.
46. How do you inject a service into a controller in AngularJS?
    • You can inject a service into a controller by specifying it as a parameter in the controller function.
47. What is the role of the $inject property in AngularJS dependency injection?
    • The $inject property is used to explicitly specify the dependencies for a component, which can be helpful when minification is applied.
48. Explain the concept of circular dependency in AngularJS.
    • Circular dependencies occur when two or more services depend on each other, which can lead to runtime errors.
49. How can you resolve circular dependencies in AngularJS?
    • Circular dependencies can be resolved by using $injector.get() to defer the injection of a service until it is needed.
50. What is the purpose of the $provide service in AngularJS?
    • The $provide service is used to configure and define services, factories, and providers.

Routing:

51. What is routing in AngularJS?
    • Routing is a mechanism in AngularJS for defining navigation and views based on URLs.
52. How do you configure routing in AngularJS?
    • Routing is configured using the $routeProvider or the $stateProvider service to define routes, templates, and controllers.
53. What is a route in AngularJS?
    • A route is a URL path mapped to a specific template and controller.
54. What is a route parameter in AngularJS?
    • Route parameters are placeholders in URLs that can capture dynamic values and pass them to a controller.
55. Explain the concept of nested routes in AngularJS.
    • Nested routes allow you to define child routes within a parent route, creating a hierarchical navigation structure.
56. How do you set up and navigate to routes in AngularJS?
    • Routes are set up in the configuration phase using $routeProvider or $stateProvider, and navigation is achieved using links or programmatically with $location.
57. What is route resolve in AngularJS, and how does it work?
    • Route resolve is a way to ensure that certain data is available before the route is activated and the associated controller is instantiated.
58. How do you pass data between routes in AngularJS?
    • Data can be passed between routes using route parameters, custom services, or the $rootScope object.
59. What is route inheritance in AngularJS?
    • Route inheritance allows child routes to inherit properties and resolve data from their parent route.
60. What is HTML5 mode in AngularJS routing?
    • HTML5 mode allows for cleaner URLs without the hash (#) symbol, improving SEO and user experience.

Custom Directives:

61. What is a custom directive in AngularJS?
    • A custom directive is a reusable component or behavior added to an HTML element.
62. How do you create a custom directive in AngularJS?
    • A custom directive is created using the directive method and defining a directive factory function.
63. Explain the options object when creating a custom directive in AngularJS.
    • The options object includes properties like restrict, template, controller, and link for configuring the directive’s behavior and appearance.
64. What is the restrict property in a custom directive in AngularJS?
    • The restrict property specifies how the directive can be used, such as E (element), A (attribute), or C (class).
65. What is the link function in a custom directive in AngularJS?
    • The link function is responsible for registering DOM listeners and updating the DOM based on the directive’s behavior.
66. How do you isolate the scope of a custom directive in AngularJS?
    • You can isolate the scope of a directive by setting the scope property to an object in the directive definition.
67. Explain the difference between @, =, and & bindings in a custom directive’s scope.
    • @ is used for
    one-way string binding, = is used for two-way binding, and & is used to pass a function to the directive.
68. What is the transclude property in a custom directive in AngularJS?
    • transclude allows you to insert content into the directive’s template and is often used with the ng-transclude directive.
69. What is the compile function in a custom directive in AngularJS?
    • The compile function is used to modify the DOM or the directive before it’s linked to the scope and controller.
70. How do you use the require property in a custom directive in AngularJS?
    • The require property specifies which controllers to require from other directives on the same element.

Filters:

71. What is a filter in AngularJS?
    • A filter is a function that formats, transforms, or filters data in an AngularJS expression.
72. How do you use built-in filters in AngularJS?
    • Built-in filters are used in expressions with the | symbol, such as {{ data | filterName }}.
73. Explain the filter filter in AngularJS.
    • The filter filter is used to filter an array based on a specified criteria.
74. What is the orderBy filter used for in AngularJS?
    • The orderBy filter sorts an array based on a specified property and order.
75. What is the currency filter in AngularJS?
    • The currency filter formats a number as currency using a specified currency symbol.
76. Explain the date filter in AngularJS.
    • The date filter formats a date object as a string with a specified format.
77. What is the uppercase and lowercase filter used for in AngularJS?
    • The uppercase filter converts a string to uppercase, while the lowercase filter converts it to lowercase.
78. How do you create a custom filter in AngularJS?
    • A custom filter is created using the filter method and returning a function that defines the filter’s behavior.
79. What is the json filter used for in AngularJS?
    • The json filter formats an object as a JSON string.
80. What is the limitTo filter in AngularJS?
    • The limitTo filter limits an array or string to a specified number of elements or characters.

Testing:

81. What is unit testing in AngularJS?
    • Unit testing in AngularJS involves testing individual components, such as controllers, services, and directives, in isolation.
82. How do you set up unit tests in AngularJS?
    • Unit tests are typically set up using testing frameworks like Jasmine and testing utilities like Karma.
83. What is end-to-end (E2E) testing in AngularJS?
    • E2E testing in AngularJS involves testing the entire application from the user’s perspective, simulating real user interactions.
84. How do you set up E2E tests in AngularJS?
    • E2E tests can be set up using tools like Protractor, which automates user interactions in a real browser.
85. What is dependency injection in the context of testing AngularJS components?
    • Dependency injection in testing allows you to provide mock or stub dependencies for a component, isolating it from external services.
86. Explain the role of the beforeEach and it functions in Jasmine testing in AngularJS.
    • beforeEach is used to set up common test conditions, and it defines individual test cases.
87. How do you mock dependencies in AngularJS unit tests?
    • Dependencies can be mocked using Jasmine’s spy functions or by providing custom implementations.
88. What is test-driven development (TDD) in AngularJS?
    • TDD is a development approach in which tests are written before code, ensuring that the code meets the expected requirements.
89. What is the role of assertions in unit testing in AngularJS?
    • Assertions are used to verify that the actual behavior of a component matches the expected behavior defined in the test.
90. How do you perform asynchronous testing in AngularJS unit tests?
    • Asynchronous tests can be handled using Jasmine’s done function, promises, or $timeout to wait for async operations.

AngularJS 1.x vs. Angular (Angular 2+):

91. What are the key differences between AngularJS 1.x and Angular (Angular 2+)?
    • Major differences include the use of TypeScript, a component-based architecture, and the absence of controllers in Angular.
92. How does Angular handle two-way data binding differently from AngularJS?
    • Angular uses property binding and event binding to achieve two-way data binding, while AngularJS uses ng-model.
93. What is the difference in the component structure between AngularJS and Angular?
    • Angular is based on components, while AngularJS uses controllers and directives.
94. How does Angular handle routing compared to AngularJS?
    • Angular uses the Angular Router module, which is more powerful and configurable than AngularJS’s $routeProvider.
95. What is the difference in dependency injection between AngularJS and Angular?
    • Angular’s dependency injection is more hierarchical and flexible, while AngularJS relies on $injector for injection.
96. How does Angular 2+ support static type checking compared to AngularJS?
    • Angular 2+ uses TypeScript for static type checking, providing better tooling and compile-time error checking.
97. What is the difference in the change detection mechanism between AngularJS and Angular?
    • Angular uses a zone.js-based change detection mechanism, which is more efficient than AngularJS’s digest cycle.
98. How does Angular handle forms and validation differently from AngularJS?
    • Angular uses a reactive approach with the FormsModule for handling forms and validation, while AngularJS uses the ng-form directive and $valid properties.
99. What are some migration strategies for moving from AngularJS to Angular (Angular 2+)?
    • Strategies include incremental migration, running AngularJS and Angular side by side, and upgrading individual components.
100. How does Angular’s development environment and tooling differ from AngularJS?
     • Angular offers improved tooling, such as the Angular CLI, for generating and managing projects, making it more developer-friendly.