Top 100 Angular Interview Questions and Answers

 

1. What is Angular?

   Angular is a TypeScript-based open-source web application framework used for building dynamic web applications.

2. What are the advantages of using Angular?

   The advantages of using Angular are:

• Increased productivity
• Reusability of code
• Enhanced testing capabilities
• Improved performance
• Enhanced security features
• Better user experience

3. What are the key features of Angular?

The key features of Angular are:

• Two-way data binding
• Dependency injection
• Templates
• Directives
• Services
• Routing
• Forms
• Animations

4. What is TypeScript?

   TypeScript is a superset of JavaScript that adds optional static typing, classes, and interfaces to the language.

5. What is the difference between AngularJS and Angular?

   AngularJS is the older version of the Angular framework, while Angular is the newer version. Angular is a complete rewrite of AngularJS and has many new features and improvements over AngularJS.

6. What is a component in Angular?

   A component in Angular is a building block of an application that controls a portion of the user interface and interacts with other components.

7. What is a template in Angular?

   A template in Angular is an HTML file that defines the user interface of a component.

8. What is a directive in Angular?

   A directive in Angular is a marker on an HTML element that tells Angular to do something with that element.

9. What is a service in Angular?

   A service in Angular is a class that provides some functionality to other parts of the application.

10. What is dependency injection in Angular?

    Dependency injection in Angular is a design pattern that allows a class to receive its dependencies from an external source rather than creating them itself.

11. What is a module in Angular?

    A module in Angular is a container for a group of related components, directives, and services.

12. What is the use of ngOnInit() in Angular?

    ngOnInit() is a lifecycle hook in Angular that is called after the component has been initialized and its inputs have been bound.

13. What is the use of ngFor directive in Angular?

    ngFor directive is used to loop over an array of items and render them in the user interface.

14. What is a reactive form in Angular?

    A reactive form in Angular is a form that is built using reactive programming techniques.

15. What is the use of HttpClient in Angular?

    HttpClient in Angular is a service that allows the application to make HTTP requests to a server.

16. What is the use of ng-content in Angular?

    ng-content in Angular is used to project content from a parent component into a child component.

17. What is a resolver in Angular?

    A resolver in Angular is a service that is used to fetch data from a server before the route is activated.

18. What is a guard in Angular?

    A guard in Angular is a service that is used to control access to a route based on certain conditions.

19. What is Angular CLI?

    Angular CLI is a command-line interface tool that is used to create, manage, and build Angular applications.

20. What is Ahead-of-Time (AOT) compilation in Angular?

    Ahead-of-Time (AOT) compilation in Angular is a process that compiles Angular templates and components into optimized JavaScript code during the build process.

21. What is Lazy Loading in Angular?

    Lazy Loading in Angular is a technique that loads only the required modules and components when they are needed, rather than loading the entire application at once.

22. What is NgZone in Angular?

    NgZone in Angular is a service that provides a way to execute code outside the Angular zone, which helps to improve performance.

23. What is Change Detection in Angular?

    Change Detection in Angular is a process that detects changes to the data model and updates the user interface accordingly.

24. What is an Observable in Angular?

    An Observable in Angular is a representation of a stream of data that can be observed and acted upon.

25. What is the difference between a Promise and an Observable?

    A Promise is a one-time operation that returns a single value, while an Observable is a stream of data that can be subscribed to and acted upon multiple times.

26. What is a Subject in Angular?

    A Subject in Angular is a type of Observable that allows data to be multicast to many observers.

27. What is a BehaviorSubject in Angular?

    A BehaviorSubject in Angular is a type of Subject that stores the current value and emits it to new subscribers.

28. What is the difference between a BehaviorSubject and a ReplaySubject?

    A BehaviorSubject stores the current value and emits it to new subscribers, while a ReplaySubject stores a buffer of previous values and can replay them to new subscribers.

29. What is NgRx in Angular?

    NgRx in Angular is a state management library that implements the Redux pattern using Observables.

30. What is Redux in Angular?

    Redux in Angular is a pattern for managing application state using a single immutable store and pure functions to update it.

31. What is Angular Universal?

    Angular Universal is a server-side rendering solution for Angular applications that allows them to be pre-rendered and served to clients as static HTML.

32. What is a resolver in Angular routing?

    A resolver in Angular routing is a service that is used to fetch data from a server before the route is activated.

33. What is canActivate guard in Angular?

    The canActivate guard in Angular is a service that is used to control access to a route based on certain conditions.

34. What is the difference between canActivate and canLoad guards in Angular?

    The canActivate guard controls access to a route based on certain conditions, while the canLoad guard controls whether a lazy-loaded module should be loaded.

35. What is Angular Material?

    Angular Material is a UI component library for Angular that provides pre-built components such as buttons, forms, dialogs, and navigation menus.

36. What is Angular Bootstrap?

    Angular Bootstrap is a UI component library for Angular that provides pre-built components such as alerts, modals, and dropdowns.

37. What is Angular Flex Layout?

    Angular Flex Layout is a library that provides a flexible layout system for Angular applications using CSS Flexbox and Grid.

38. What is the difference between ViewChild and ContentChild in Angular?

    ViewChild is used to get a reference to a child component or element, while ContentChild is used to get a reference to a child element that is projected into the component.

39. What is the difference between ngOnChanges and ngOnInit in Angular?

    ngOnChanges is called whenever a component input property changes, while ngOnInit is called once after the component is initialized.

40. What is the difference between ng-template and ng-container in Angular?

    ng-template is used to define a reusable template that can be used in multiple places, while ng-container is used as a placeholder for content that is not being rendered.

41. What is the use of ngZone.run() in Angular?

    ngZone.run() is used to execute code within the Angular zone, which triggers change detection and updates the user interface.

42. What is the difference between ngClass and ngStyle in Angular?

    ngClass is used to apply CSS classes dynamically based on conditions, while ngStyle is used to apply inline styles dynamically based on conditions.

43. What is the difference between ViewEncapsulation and Shadow DOM in Angular?

    ViewEncapsulation is a way to isolate component styles from the rest of the application, while Shadow DOM is a web platform feature that allows for true DOM encapsulation.

44. What is the use of trackBy function in ngFor directive in Angular?

    The trackBy function is used to improve the performance of ngFor by identifying unique items in

45. What is the difference between ng-content and ng-template in Angular?

    ng-content is used to project content into a component, while ng-template is used to define a reusable template that can be used in multiple places.

46. What is a pure pipe in Angular?

    A pure pipe in Angular is a type of pipe that only runs when its input value changes, and does not rely on external state.

47. What is an impure pipe in Angular?

    An impure pipe in Angular is a type of pipe that runs whenever change detection runs, regardless of whether its input value has changed.

48. What is the difference between a pure and impure pipe in Angular?

    A pure pipe only runs when its input value changes, while an impure pipe runs whenever change detection runs, regardless of whether its input value has changed.

49. What is a custom validator in Angular?

    A custom validator in Angular is a function that is used to validate the contents of a form control.

50. What is a custom directive in Angular?

    A custom directive in Angular is a type of directive that can be used to modify the behavior or appearance of an element.

51. What is a structural directive in Angular?

    A structural directive in Angular is a type of directive that can be used to modify the structure of the DOM.

52. What is the difference between a component and a directive in Angular?

    A component is a type of directive that has a template and can be used as a standalone element, while a directive is a generic term for any type of Angular directive.

53. What is the difference between an attribute directive and a structural directive in Angular?

    An attribute directive modifies the behavior or appearance of an element, while a structural directive modifies the structure of the DOM.

54. What is a lazy-loaded module in Angular?

    A lazy-loaded module in Angular is a module that is loaded on demand, rather than being loaded as part of the initial application bundle.

55. What is the difference between an NgModule and a regular module in Angular?

    An NgModule is a special type of module in Angular that is used to organize components, directives, and services into a cohesive unit.

56. What is the difference between a provider and a service in Angular?

    A provider is a token that maps to a service, while a service is a class that provides functionality to other parts of an application.

57. What is the difference between a singleton and a scoped service in Angular?

    A singleton service is a service that is created once and shared across the entire application, while a scoped service is created once per component instance.

58. What is the difference between an ElementRef and a TemplateRef in Angular?

    An ElementRef is a reference to the host element of a component or directive, while a TemplateRef is a reference to a template that can be used to create a view.

59. What is a view in Angular?

    A view in Angular is a combination of a component and a template that is used to create a section of the user interface.

60. What is a component factory in Angular?

    A component factory in Angular is a type of factory that is used to create instances of components dynamically.

61. What is the difference between an entry component and a regular component in Angular?

    An entry component is a component that is created dynamically, while a regular component is created as part of the application's initial bootstrapping process.

62. What is the difference between ngOnChanges and ngDoCheck in Angular?

    ngOnChanges is called whenever a component input property changes, while ngDoCheck is called whenever change detection runs.

63. What is the use of ElementRef in Angular?

    ElementRef is a reference to the host element of a component or directive that can be used to interact with the element directly.

64. What is a ViewChild decorator in Angular?

    The ViewChild decorator in Angular

65. What is a ContentChild decorator in Angular?

    The ContentChild decorator in Angular is used to get a reference to an element or directive within the content of a component.

66. What is a directive in Angular?

    A directive in Angular is a way to attach behavior or modify the appearance of an element.

67. What is a component in Angular?

    A component in Angular is a combination of a template and a class that controls a section of the user interface.

68. What is dependency injection in Angular?

    Dependency injection in Angular is a way to provide dependencies to a class or component without creating them directly.

69. What is a service in Angular?

    A service in Angular is a class that provides functionality to other parts of an application.

70. What is a module in Angular?

    A module in Angular is a way to organize components, directives, and services into a cohesive unit.

71. What is a template in Angular?

    A template in Angular is a section of HTML that can be used to generate the user interface.

72. What is a selector in Angular?

    A selector in Angular is a way to identify which elements a directive or component should be applied to.

73. What is a decorator in Angular?

    A decorator in Angular is a special type of function that is used to modify the behavior of a class, property, or method.

74. What is a route guard in Angular?

    A route guard in Angular is a way to protect routes and prevent unauthorized access.

75. What is a resolver in Angular?

    A resolver in Angular is a way to prefetch data before a route is loaded.

76. What is the use of *ngFor directive in Angular?

    The *ngFor directive in Angular is used to generate a list of items based on an array or iterable.

77. What is the use of *ngIf directive in Angular?

    The *ngIf directive in Angular is used to conditionally show or hide elements based on a boolean expression.

78. What is the use of [(ngModel)] directive in Angular?

    The [(ngModel)] directive in Angular is used to bind a form control to a property in the component.

79. What is the use of @ViewChild decorator in Angular?

    The @ViewChild decorator in Angular is used to get a reference to an element or directive within the template of a component.

80. What is the use of @ContentChild decorator in Angular?

    The @ContentChild decorator in Angular is used to get a reference to an element or directive within the content of a component.

81. What is the use of @Input decorator in Angular?

    The @Input decorator in Angular is used to define an input property for a component.

82. What is the use of @Output decorator in Angular?

    The @Output decorator in Angular is used to define an output event for a component.

83. What is the use of ngOnInit in Angular?

    ngOnInit is a lifecycle hook in Angular that is called after the component has been initialized.

84. What is the use of ngOnDestroy in Angular?

    ngOnDestroy is a lifecycle hook in Angular that is called just before the component is destroyed.

85. What is the use of ngAfterViewInit in Angular?

    ngAfterViewInit is a lifecycle hook in Angular that is called after the component's view has been initialized.

86. What is the use of ngAfterViewChecked in Angular?

    ngAfterViewChecked is a lifecycle hook in Angular that is called after the component's view has been checked.

87. What is the use of ngAfterContentInit in Angular?

    ngAfterContentInit is a lifecycle hook in Angular that is called after the component's content has been initialized.

88. What is the use of ngAfterContentChecked in Angular?

    ngAfterContentChecked is a lifecycle hook in Angular that is called after the component's content has been checked.

89. What is an Observable in Angular?

    An Observable in Angular is a way to handle asynchronous data streams, allowing for reactive programming and real-time updates.

90. What is a Subject in Angular?

    A Subject in Angular is a type of Observable that allows for multicast communication, enabling multiple subscribers to receive the same data stream.

91. What is a BehaviorSubject in Angular?

    A BehaviorSubject in Angular is a type of Subject that always returns the current value upon subscription, even if no data has been emitted yet.

92. What is an EventEmitter in Angular?

    An EventEmitter in Angular is a way to emit custom events from a component, which can be subscribed to and handled in other parts of the application.

93. What is a pipe in Angular?

    A pipe in Angular is a way to transform data before displaying it in the user interface.

94. What is the use of async pipe in Angular?

    The async pipe in Angular is used to handle asynchronous data streams, automatically subscribing and unsubscribing as needed.

95. What is the use of the ng-template directive in Angular?

    The ng-template directive in Angular is used to define a template that can be reused in multiple parts of a component.

96. What is the use of the ng-container directive in Angular?

    The ng-container directive in Angular is used to group multiple elements together without adding an extra DOM element.

97. What is the use of the ng-content directive in Angular?

    The ng-content directive in Angular is used to project content from the parent component into the child component.

98. What is the use of the ngStyle directive in Angular?

    The ngStyle directive in Angular is used to dynamically set the style of an element based on a property in the component.

99. What is the use of the ngClass directive in Angular?

    The ngClass directive in Angular is used to dynamically set the class of an element based on a property in the component.

100. What is the use of the ng-template outlet directive in Angular?

     The ng-template outlet directive in Angular is used to insert a template into the DOM at a specific location, allowing for dynamic content insertion.

101. What is a resolver in Angular?

     A resolver in Angular is a service that pre-fetches data for a route before the component is rendered, ensuring that the component has all the necessary data it needs to function.

102. What is a guard in Angular?

     A guard in Angular is a service that can be used to prevent unauthorized access to certain routes or features, based on certain conditions.

103. What is the use of the RouterLink directive in Angular?

     The RouterLink directive in Angular is used to navigate to a different route within the application when the user clicks on a link or button.

104. What is the use of the ActivatedRoute service in Angular?

     The ActivatedRoute service in Angular is used to retrieve information about the currently activated route, such as route parameters and query strings.

105. What is the use of the Router service in Angular?

     The Router service in Angular is used to programmatically navigate to a different route within the application.

106. What is the use of the CanActivate interface in Angular?

     The CanActivate interface in Angular is used to define a guard that can be used to prevent unauthorized access to a certain route based on certain conditions.

107. What is the use of the CanDeactivate interface in Angular?

     The CanDeactivate interface in Angular is used to define a guard that can be used to prevent the user from leaving a certain page or component based on certain conditions.

108. What is the use of the CanLoad interface in Angular?

     The CanLoad interface in Angular is used to define a guard that can be used to prevent the lazy loading of a module based on certain conditions.

109. What is the use of the RouterModule in Angular?

     The RouterModule in Angular is used to set up the application's routing configuration and enable navigation between different routes.

110. What is the use of the HttpClient service in Angular?

     The HttpClient service in Angular is used to make HTTP requests to a server and handle the response data.