Angular Interview Questions And Answers
Angular Interview Questions For Freshers
1. What is Angular?
Answer: Angular is a platform and framework for building client-side applications using HTML, CSS, and JavaScript/TypeScript.
2. What are the main features of Angular?
Answer: Key features include modularity, dependency injection, two-way data binding,
3. What is a component in Angular?
Answer: A component is a basic building block of an Angular application, controlling a portion of the UI.
4. What is the Angular CLI?
Answer: Angular CLI is a command-line tool used to scaffold and manage Angular projects.
5. What are services in Angular?
Answer: Services are reusable classes that handle logic, data fetching, and interaction with APIs, and they are injected into components via Dependency Injection.
6. What is Dependency Injection (DI)?
Answer: DI is a design pattern in which a class receives its dependencies from an external source rather than creating them internally.
7. Explain two-way data binding in Angular.
Answer: Two-way data binding automatically synchronizes data between the model and the view.
8. What are Angular modules?
Answer: Modules are containers for components, services, pipes, and other related code, grouped together to organize an Angular application.
9. What is a directive in Angular?
Answer: Directives are special markers in the DOM that tell Angular to execute certain behavior.
10.What is the difference between structural and attribute directives?
Answer: Structural directives change the structure of the DOM, while attribute directives change the appearance or behavior of an element.
11. What is NgModule?
Answer: NgModule is a decorator that defines a module, declaring which components and services belong to the module.
12. What is a template in Angular?
Answer: A template is the HTML that defines the view for an Angular component.
13. Explain the role of @Input() and @Output() decorators.
Answer: @Input() allows a parent component to pass data to a child component. @Output() allows the child component to send data back to the parent component
14. What is an Angular Router?
Answer: The Angular Router is used for navigating between different components and views in an Angular application.
15. What is a pipe in Angular?
Answer: A pipe is used to transform data in a template, such as formatting dates or filtering data.
16. What is the difference between ngOnInit() and a constructor?
Answer: The constructor initializes the component, while ngOnInit() is a lifecycle hook called after the component is initialized, where you should place initialization logic.
17. What are lifecycle hooks in Angular?
Answer: Lifecycle hooks are methods that Angular calls at various stages of a component’s lifecycle, such as initialization (ngOnInit), changes detection (ngOnChanges), and destruction (ngOnDestroy).
18. What is RxJS in Angular?
Answer: RxJS is a library for reactive programming using Observables, enabling powerful async programming.
19. What is the purpose of ngModel?
Answer: ngModel is used for two-way data binding in template-driven forms.
20. What are Angular Forms?
Answer: Angular Forms are used for handling user inputs, validating, and processing forms, either template-driven or reactive forms.
21. What is interpolation in Angular?
Answer: Interpolation is the process of binding data from the component to the view using {{}} syntax.
22. Explain the ngIf directive.
Answer: ngIf conditionally includes or excludes elements from the DOM based on a Boolean expression.
23. What is the role of ngFor in Angular?
Answer: ngFor is used to iterate over an array or object and render items dynamically in the view.
24. How does Angular handle error handling?
Answer: Angular uses HTTP interceptors, try-catch blocks, and global error handlers (ErrorHandler) to manage errors.
25. What is the role of HttpClient in Angular?
Answer: HttpClient is a service used to make HTTP requests and handle responses in Angular applications.
26. What is the purpose of environment files in Angular?
Answer: Environment files store different configuration settings for different environments (e.g., development and production).
27. What is an observable in Angular?
Answer: Observables are used to handle asynchronous data streams in Angular, allowing for the management of events like HTTP requests.
28. How do you create a custom directive in Angular?
Answer: By using the @Directive() decorator and implementing required logic for the directive.
29. What is the difference between Angular and AngularJS?
Answer: Angular is a complete rewrite of AngularJS, based on TypeScript, with improved architecture, performance, and modularity.
30. What are reactive forms in Angular?
Answer: Reactive forms are forms that are more programmatically driven and are built using FormControl, FormGroup, and FormBuilder.
Angular Interview Questions for Experienced
31. How do you optimize Angular applications?
Answer: Techniques include lazy loading modules, using change detection strategies, ahead-of-time (AOT) compilation, and tree-shaking.
32. What is Ahead-of-Time (AOT) Compilation in Angular?
Answer: AOT compiles Angular templates during the build process, reducing the size of the bundle and improving application startup time.
33. Explain Change Detection Strategy in Angular.
Answer: Change detection strategies, such as OnPush, help optimize performance by limiting how often components check for changes.
34. What is lazy loading in Angular?
Answer: Lazy loading is a technique where modules are loaded on demand rather than at the start of the application, improving performance.
35. How do you handle authentication in Angular?
Answer: Using HttpClient, JWT (JSON Web Tokens), route guards, and services to handle user authentication and authorization.
36. What is the difference between Promise and Observable in Angular?
Answer: Promises handle a single async operation, while Observables allow multiple values and offer more operators for complex scenarios like retrying and canceling.
37. How do you implement routing guards in Angular?
Answer: Routing guards like CanActivate, CanDeactivate, and CanLoad are used to control access to routes based on logic.
38. What is the purpose of Angular’s NgZone?
Answer: NgZone allows Angular to detect changes outside of its own boundary, such as external libraries, improving performance.
39. What is the role of the Renderer2 service?
Answer: Renderer2 is used for safely manipulating DOM elements in Angular, especially in web workers.
40. Explain Angular’s Dependency Injection Hierarchy.
Answer: Angular has a hierarchical injector, meaning child injectors inherit dependencies from parent injectors, making DI more modular.
41. What is the Angular Service Worker?
Answer: The Angular Service Worker allows Angular apps to work offline by caching files and serving them when offline.
42. What are HttpInterceptors in Angular?
Answer: HttpInterceptors are used to modify or log HTTP requests and responses, handling authentication tokens and error handling.
43. Explain Angular animations.
Answer: Angular animations use the @angular/animations module to define animations using triggers, states, and transitions in components.
44. What is NgRx in Angular?
Answer: NgRx is a state management library for Angular, based on Redux, used to manage global application state.
45. What are view encapsulation options in Angular?
Answer: Angular provides three view encapsulation modes: Emulated, Native, and None, which control the styling scope.
46. How do you protect routes with CanActivate and CanDeactivate?
Answer: CanActivate prevents access to a route, and CanDeactivate prevents leaving a route, based on logic or conditions.
47. How do you share data between components in Angular?
Answer: Data can be shared using @Input(), @Output(), services, and the EventEmitter class.
48. What is differential loading in Angular?
Answer: Differential loading is a technique where Angular creates different bundles for modern and legacy browsers, optimizing performance.
49. How do you implement server-side rendering (SSR) in Angular?
Answer: SSR can be implemented using Angular Universal, which renders the app on the server to improve SEO and load time.
50. How do you secure an Angular application?
Answer: Security practices include using route guards, encoding/escaping user input, enabling CORS, and using secure HTTP-only cookies for sensitive data.
51. What is the role of ng-content in Angular?
Answer: ng-content is used to project content from a parent component into a child component, enabling content projection.
52. How do you create custom pipes in Angular?
Answer: Custom pipes can be created using the @Pipe() decorator and implementing the transform() method to define the logic.
53. What are Angular’s entry components?
Answer: Entry components are components that Angular loads dynamically, often used with modals or dynamically generated components.
54. How do you manage global error handling in Angular?
Answer: Global error handling is done by implementing the ErrorHandler class and creating a custom global error handler service.
55. What is the Angular Ivy renderer?
Answer: Ivy is Angular’s latest rendering engine, which optimizes application size and performance by tree-shaking and code splitting.
56. How do you optimize Angular applications for SEO?
Answer: SEO can be improved using server-side rendering (SSR) with Angular Universal, meta tags, and lazy loading modules.
57. What is the ng-container in Angular?
Answer: ng-container is a logical container that doesn’t render a DOM element but allows grouping of multiple elements.
58. What is dynamic component loading in Angular?
Answer: Dynamic component loading involves creating components programmatically using ComponentFactoryResolver and ViewContainerRef.
59. How do you handle file uploads in Angular?
Answer: File uploads can be managed using HttpClient, FormData, and services that interact with an API to upload files to a server.
60. What is the purpose of trackBy in Angular ngFor?
Answer: trackBy improves the performance of ngFor by tracking elements and preventing unnecessary re-renders when the array changes.
61. What are Angular Resolvers?
Answer: Resolvers fetch data before navigating to a route, ensuring that the route data is available before the component is activated.
62. Explain Angular’s injector tree.
Answer: Angular’s injector tree is hierarchical, where child components can inherit dependencies from parent components, enabling modular DI.
63. What is the async pipe in Angular?
Answer: The async pipe subscribes to Observables and Promises directly in the template, automatically unsubscribing when the component is destroyed.
64. How do you implement multi-language support (i18n) in Angular?
Answer: Angular supports internationalization (i18n) through built-in tools that allow the app to be translated into different languages using translation files.
65. What is Angular’s RendererFactory2?
Answer: RendererFactory2 allows you to create multiple renderers that manipulate the DOM and interact with Web Workers and native platform services.
66. How does Angular handle security vulnerabilities like XSS?
Answer: Angular provides built-in sanitization mechanisms to prevent XSS (cross-site scripting) attacks by escaping dangerous HTML in templates.
67. What is the role of Angular zones (NgZone)?
Answer: Zones in Angular are used to detect asynchronous operations and trigger change detection when these operations complete.
68. How do you implement OAuth or social login in Angular?
Answer: OAuth or social login can be implemented using external libraries like angular-oauth2-oidc, combined with HTTP interceptors for token management.
69. What is Angular Universal?
Answer: Angular Universal is a tool for server-side rendering (SSR) of Angular applications, improving performance and SEO.
70. What is differential loading in Angular?
Answer: Differential loading automatically generates separate bundles for modern and legacy browsers, optimizing performance for both types of browsers.
71. What is Angular’s FormBuilder?
Answer: FormBuilder is a service that simplifies the creation of reactive forms by providing a flexible API to handle form control groups and validations.
72. What is an Angular route guard, and what types are available?
Answer: Route guards control access to routes based on logic or conditions. Available types include CanActivate, CanDeactivate, Resolve, and CanLoad.
73. Explain the difference between an observable and a subject in Angular.
Answer: Observables emit values over time, while subjects are observables that can emit multiple values and allow multiple subscribers.
74. What is ControlValueAccessor in Angular forms?
Answer: ControlValueAccessor is an interface that enables integration of custom form controls into Angular’s forms API
75. How do you use the NgTemplateOutlet directive in Angular?
Answer: NgTemplateOutlet allows dynamic rendering of templates based on a reference passed to it, enabling template reuse.
76. How do you implement state management in Angular using NgRx?
Answer: NgRx uses the Redux pattern for state management, where the state is stored in a single object and is mutated only through actions and reducers.
77. Explain the role of Actions, Reducers, and Effects in NgRx.
Answer: Actions describe events, Reducers define how the state changes in response, and Effects handle side effects like API calls.
78. How do you handle complex forms in Angular?
Answer: Complex forms can be handled using Reactive Forms with FormGroup, FormArray, and custom validators.
79. What is memoization in Angular, and how does it help with performance?
Answer: Memoization caches the result of function calls to avoid redundant recalculations, improving the performance of components.
80. Explain the difference between eager loading and lazy loading modules in Angular.
Answer: Eager loading loads all modules upfront, while lazy loading loads modules on demand when a specific route is accessed.
81. How do you debug Angular applications efficiently?
Answer: Use tools like Augury, Chrome Developer Tools, and Angular CLI debugging flags like –source-map for inspecting components and services.
82. How do you manage inter-component communication in a large-scale Angular application?
Answer: Communication is managed using services, EventEmitter, or global state management solutions like NgRx or Akita.
83. What is content projection in Angular, and how does it work?
Answer: Content projection allows a component to display content passed from its parent component using <ng-content>.
84. How do you handle route transitions in Angular with animations?
Answer: Angular provides a built-in animations module to define transitions between routes using triggers, states, and transitions.
85. How do you optimize Angular applications for a production build?
Answer: Use AOT compilation, lazy loading, OnPush change detection strategy, and production flags during the build process.
86. What is the use of decorators in Angular?
Answer: Decorators such as @Component, @Injectable, @Pipe, and @Directive add metadata to classes, enabling Angular to process them appropriately.
87. What is the role of ControlContainer in Angular forms?
Answer: ControlContainer provides access to the parent form group or form array when dealing with nested forms.
88. What is ViewChildren and ContentChildren in Angular?
Answer: ViewChildren queries child elements in the view, while ContentChildren queries child elements projected into a component via ng-content.
89. What is route preloading in Angular?
Answer: Route preloading fetches lazy-loaded modules in the background after the initial app load to improve navigation performance.
90. Explain how Angular ensures backward compatibility in version updates.
Answer: Angular uses semantic versioning, deprecating features gradually while providing backward compatibility for most minor version updates.
91. How do you create a multi-module Angular application?
Answer: Use Angular CLI to generate modules, group related components, services, and routes into feature modules, and lazy load them.
92. What is custom form validation in Angular, and how is it implemented?
Answer: Custom validation involves creating functions that return validation logic for forms, applied using Validators.compose or directly in reactive forms.
93. How does Angular handle large datasets in the view?
Answer: Angular provides optimizations like virtual scrolling (via cdk-virtual-scroll-viewport), pagination, and infinite scroll to handle large datasets.
94. What is the purpose of ng-template in Angular?
Answer: ng-template is used to define a template that can be rendered dynamically based on the logic provided in the component.
95. What is the benefit of using Angular Elements?
Answer: Angular Elements allow Angular components to be packaged as custom web elements, which can be used in any web framework.
Angular Interview Questions for 5 years Experience
96. How does Angular improve the bundle size during build?
Answer: Angular uses techniques like tree-shaking, differential loading, and Ahead-of-Time (AOT) compilation to reduce the bundle size.
97. How do you implement authentication guards in Angular?
Answer: Use CanActivate and CanLoad guards to restrict access to routes based on user roles or authentication status.
98. What is Angular Schematics?
Answer: Schematics are templates used by Angular CLI to scaffold components, services, and other project structures automatically.
99. How do you handle performance bottlenecks in Angular apps?
Answer: Identify and optimize issues using Chrome’s Performance tab, lazy loading, AOT compilation, ChangeDetectionStrategy, and optimizing HTTP requests.