Angular Interview Questions -Level 2
Total of 100 angular advance questions with answers
General Angular Concepts
- What is the purpose of Angular’s platform-server package?
Ans: The platform-server package allows Angular applications to be run on a server, providing the ability to generate static HTML content for each route.
2. Explain Angular Universal and its benefits.
Ans: Angular Universal is a technology that allows server-side rendering of Angular applications. Benefits include improved SEO, faster initial load times, and better performance on low-powered devices.
3. What are Angular schematics, and how do they work?
Ans: Angular schematics are templates used by the Angular CLI to generate or modify code. They automate tasks like creating components, modules, and services.
4. Describe Angular’s Ahead-of-Time (AOT) compilation.
Ans: AOT compilation converts Angular TypeScript code into efficient JavaScript code during the build process, reducing the size of the final bundle and improving runtime performance.
5. What is Ivy, and what are its advantages?
Ans: Ivy is Angular’s new rendering engine introduced in version 9. It provides smaller bundle sizes, faster compilation, better debugging, and improved runtime performance.
Components and Templates
6. Explain the role of Angular decorators.
Ans: Angular decorators like @Component, @Directive, @Injectable, and @NgModule provide metadata that Angular uses to understand and process the classes they decorate.
7. What is the difference between a template-driven form and a reactive form in Angular?
Ans: Template-driven forms are simpler and rely on directives in the template, whereas reactive forms provide more control and validation logic through an explicit model in the component.
8. How do you create a custom directive in Angular?
Ans: Use the @Directive decorator to create a custom directive, and implement necessary lifecycle hooks like ngOnInit to add behavior to DOM elements.
9. What is ViewEncapsulation in Angular, and what are its modes?
Ans: ViewEncapsulation defines how styles are applied to components. Modes include Emulated (default), None, and ShadowDom.
10. How can you dynamically create a component in Angular?
Ans: Use ComponentFactoryResolver and ViewContainerRef to dynamically create and inject components at runtime.
Dependency Injection
11. Explain Angular’s dependency injection (DI) system.
Ans: Angular’s DI system allows the creation and injection of services into components or other services, promoting modularity and testability.
12. What is a provider in Angular?
Ans: A provider defines how an injectable dependency is created. Providers are configured in modules, components, or services.
13. What is the difference between useClass, useExisting, useValue, and useFactory in Angular providers?
Ans: useClass provides a class, useExisting provides an existing service, useValue provides a static value, and useFactory provides a service created by a factory function.
14. How can you inject a service into a directive or pipe?
Ans: Use the @Injectable decorator on the service and inject it into the directive or pipe via the constructor.
15. What are multi providers in Angular?
Ans: Multi providers allow multiple values to be provided for a single token, useful for creating extensible frameworks or plugins.
Routing
16. How do you lazy load a module in Angular?
Ans: Use the loadChildren property in the route configuration to lazy load a module using dynamic import syntax.
17. Explain Angular’s route guards and their types.
Ans: Route guards control access to routes. Types include CanActivate, CanActivateChild, CanDeactivate, CanLoad, and Resolve.
18. How do you implement a custom preloading strategy in Angular?
Ans: Create a class that implements PreloadingStrategy and override the preload method to define custom logic for preloading modules.
19. What is the purpose of the RouterModule.forRoot() and RouterModule.forChild() methods?
Ans: forRoot() configures the main application routes, while forChild() configures routes for feature modules.
20. How do you pass data to a route in Angular?
Ans: Use route parameters, query parameters, or static data in the route configuration to pass data to a route.
Services and HTTP Client
21. Explain the role of interceptors in Angular’s HTTP client.
Ans: Interceptors allow you to modify HTTP requests and responses globally, useful for adding headers, logging, or error handling.
22. How can you handle HTTP errors in Angular?
Ans: Use the catchError operator from RxJS to handle HTTP errors in a service or component.
23. What is the purpose of the HttpClientModule, and how do you configure it?
Ans: HttpClientModule provides HTTP services. Import it in the root module and inject HttpClient into services or components.
24. How do you implement retry logic for HTTP requests in Angular?
Ans: Use the retry operator from RxJS to automatically retry failed HTTP requests a specified number of times.
25. What is JSONP, and how do you use it in Angular?
Ans: JSONP is a technique for requesting data from a different domain. Use the JsonpClientModule and JsonpInterceptor to make JSONP requests.
State Management
26. What are the benefits of using a state management library in Angular?
Ans: Benefits include centralized state, easier debugging, predictable state transitions, and better scalability.
27. How does NgRx handle state management in Angular applications?
Ans: NgRx uses a Redux-inspired architecture with actions, reducers, selectors, and effects to manage state.
28. Explain the role of actions and reducers in NgRx.
Ans: Actions describe state changes, while reducers handle state transitions based on actions.
29. What are selectors in NgRx, and how do they work?
Ans: Selectors are pure functions used to derive and memoize state slices from the store.
30. How do you handle side effects in NgRx?
Ans: Use @ngrx/effects to handle side effects by defining effect classes that listen to actions and perform asynchronous operations.
Advanced Topics
31. What is Angular Elements, and how do you use it?
Ans: Angular Elements allows you to create custom elements (web components) from Angular components, making them usable in non-Angular environments.
32. How do you optimize the performance of an Angular application?
Ans: Techniques include AOT compilation, lazy loading, code splitting, using OnPush change detection, and optimizing third-party libraries.
33. What is the difference between a pure and impure pipe in Angular?
Ans: Pure pipes are stateless and called only when input changes, while impure pipes can change with every change detection cycle.
34. How do you implement internationalization (i18n) in Angular?
Ans: Use Angular’s built-in i18n tools, including the @angular/localize package, translation files, and i18n attributes in templates.
35. What is the purpose of Angular’s Renderer2?
Ans: Renderer2 is an abstraction for DOM manipulation, allowing safer and more platform-agnostic code.
Testing
36. How do you write unit tests for Angular components?
Ans: Use the TestBed utility to configure and create a testing module, and the ComponentFixture to test component interactions and DOM.
37. What are Angular’s testing utilities?
Ans: Key utilities include TestBed, ComponentFixture, DebugElement, and helper functions like async and fakeAsync.
38. Explain the difference between async and fakeAsync in Angular testing.
Ans: async allows asynchronous code to run naturally, while fakeAsync uses a fake time zone to control time and handle asynchronous code synchronously.
39. How do you test services with dependencies in Angular?
Ans: Use TestBed to configure a testing module and provide mocks or spies for dependencies using HttpClientTestingModule or libraries like Jasmine.
40. What is the purpose of end-to-end (E2E) testing in Angular?
Ans: E2E testing verifies the entire application flow, ensuring that components, services, and modules work together correctly. Angular uses Protractor for E2E testing.
Build and Deployment
41. How do you configure Angular CLI build options?
Ans: Use the angular.json file to configure build options like optimization, source maps, assets, and output paths.
42. What is differential loading in Angular?
Ans: Differential loading generates separate bundles for modern and legacy browsers, optimizing performance by serving smaller bundles to modern browsers.
43. How can you reduce the bundle size of an Angular application?
Ans: Techniques include AOT compilation, tree-shaking, lazy loading, removing unused dependencies, and using differential loading.
44. What is the purpose of the ng-packagr tool?
Ans: ng-packagr is a tool for packaging Angular libraries in the Angular Package Format (APF), ensuring compatibility and ease of use.
45. How do you deploy an Angular application to different environments?
Ans: Use Angular CLI’s ng build --configuration flag to build the application for different environments and configure environment-specific settings in src/environments.
Performance Optimization
46. How can you optimize Angular’s change detection strategy?
Ans: Use ChangeDetectionStrategy.OnPush to reduce change detection cycles and ngZone.runOutsideAngular to run non-Angular code outside of Angular's zone.
47. What is tree-shaking in Angular, and how does it work?
Ans: Tree-shaking is the process of removing unused code from the final bundle, enabled by ES6 modules and tools like Webpack.
48. How do you use Angular’s trackBy function in ngFor?
Ans: The trackBy function improves performance by tracking items by unique identifiers, reducing the need to re-render entire lists.
49. Explain the purpose of Angular’s @angular/compiler-cli package.
Ans: The @angular/compiler-cli package provides tools for AOT compilation, linting templates, and other build-time optimizations.
50. What are Angular’s zones, and how do they affect performance?
Ans: Zones are execution contexts that track asynchronous operations, helping Angular’s change detection. Misuse or excessive zone use can degrade performance.
Security
51. How do you protect against XSS attacks in Angular?
Ans: Angular’s built-in sanitization and security contexts (like bypassSecurityTrustHtml) help protect against XSS attacks.
52. What is Angular’s DomSanitizer, and how do you use it?
Ans: DomSanitizer is a service that sanitizes potentially unsafe values to prevent XSS attacks. Use methods like sanitize, bypassSecurityTrustHtml, and bypassSecurityTrustStyle.
53. How can you implement authentication in an Angular application?
Ans: Use JWT tokens, OAuth, or session-based authentication, and manage authentication state with services and route guards.
54. What are Angular’s content security policies (CSP), and how do you implement them?
Ans: CSPs restrict sources of content to mitigate XSS attacks. Configure CSP headers in the server and use Angular’s sanitization services.
55. How do you handle CSRF attacks in Angular?
Ans: Use anti-CSRF tokens, set the XSRF-TOKEN cookie, and configure Angular's HttpClient to automatically include the token in requests.
Advanced Topics
56. Explain Angular’s module federation and its use case.
Ans: Module federation allows dynamic code sharing between separate applications, enabling micro-frontends and lazy loading of remote modules.
57. How do you use Web Workers in Angular?
Ans: Web Workers offload CPU-intensive tasks to background threads. Use Angular CLI to generate workers and communicate with them via message passing.
58. What is Angular’s Renderer3, and how does it differ from Renderer2?
Ans: Renderer3 is the latest rendering engine in Ivy, optimized for better performance and more efficient DOM manipulation compared to Renderer2.
59. How do you debug Angular applications effectively?
Ans: Use tools like Angular DevTools, source maps, and browser developer tools. Utilize logging, breakpoints, and performance profiling to debug issues.
60. How can you create reusable libraries in Angular?
Ans: Use Angular CLI’s ng generate library command to create and package libraries, ensuring compatibility with Angular's ecosystem.
RxJS and Observables
61. What are the benefits of using RxJS in Angular?
Ans: RxJS provides powerful tools for managing asynchronous data streams, enhancing reactivity, and simplifying complex data handling.
62. Explain the difference between Subject, BehaviorSubject, ReplaySubject, and AsyncSubject in RxJS.
Ans: Subject is a basic observable, BehaviorSubject holds the latest value, ReplaySubject replays specified number of values, and AsyncSubject emits the last value upon completion.
63. How do you handle errors in RxJS streams?
Ans: Use operators like catchError, retry, and throwError to handle and recover from errors in streams.
64. What are hot and cold observables in RxJS?
Ans: Cold observables create a new producer for each subscriber, while hot observables share a single producer among subscribers.
65. How do you convert a promise to an observable in Angular?
Ans: Use the from operator to convert a promise to an observable.
Angular Material and UI Libraries
66. What is Angular Material, and how do you use it?
Ans: Angular Material is a UI component library following Google’s Material Design principles. Import modules and use components in templates to build responsive UIs.
67. How do you create a custom theme in Angular Material?
Ans: Define a custom theme using SCSS variables and mixins, and apply it globally or to specific components.
68. What are Angular CDK and its benefits?
Ans: Angular CDK provides reusable behavior and tools for building custom UI components, including accessibility, overlay, drag-and-drop, and virtual scrolling.
69. How do you use Angular Material’s data table component?
Ans: Import the MatTableModule, define columns and data sources, and use directives like mat-header-cell, mat-cell, and mat-row in templates.
70. What is the purpose of Angular Material’s Overlay module?
Ans: The Overlay module provides a flexible way to create floating panels, tooltips, dialogs, and other overlay elements.
Internationalization and Localization
71. How do you use Angular’s i18n support for localization?
Ans: Use the i18n attribute in templates, extract translation strings, and provide translation files for different languages.
72. How can you dynamically change the language in an Angular application?
Ans: Use a service to manage the current language and reload the application or specific components with the new language settings.
73. What is Angular’s LOCALE_ID, and how do you use it?
Ans: LOCALE_ID is a token that provides the current locale. Configure it in the module providers to set the locale for date, number, and currency pipes.
74. How do you handle pluralization and complex messages in Angular i18n?
Ans: Use ICU message format for handling pluralization, gender, and other complex message patterns in translation files.
75. What are the advantages of using ngx-translate for Angular localization?
Ans: ngx-translate provides dynamic language switching, easy integration with external translation services, and more flexible runtime translation capabilities.
Advanced Performance Optimization
76. How do you use Webpack customizations in Angular projects?
Ans: Customize Webpack configurations by extending Angular’s default setup using custom builders or angular-builders package.
77. What is the Angular CLI’s ng build --prod flag, and what optimizations does it perform?
Ans: The --prod flag enables AOT compilation, minification, compression, and other optimizations for production builds.
78. How do you implement service workers in Angular?
Ans: Use the @angular/service-worker package to enable PWA features like caching, offline support, and background synchronization.
79. What is pre-rendering, and how do you implement it in Angular?
Ans: Pre-rendering generates static HTML for routes at build time, improving load times and SEO. Use tools like Scully for Angular pre-rendering.
80. How do you analyze and reduce bundle size in Angular applications?
Ans: Use Webpack Bundle Analyzer or Angular CLI’s ng build --stats-json to analyze bundle content and optimize dependencies.
Advanced RxJS Techniques
81. What is backpressure in RxJS, and how do you handle it?
Ans: Backpressure occurs when a producer emits values faster than a consumer can process. Handle it using operators like buffer, throttle, debounce, and sample.
82. How do you create custom RxJS operators in Angular?
Ans: Create custom operators by defining functions that return an observable, using pipe and existing operators to manipulate streams.
83. What is the difference between switchMap, mergeMap, concatMap, and exhaustMap?
Ans: switchMap cancels previous streams, mergeMap merges all streams, concatMap concatenates streams in order, and exhaustMap ignores new streams until the current one completes.
84. How do you manage subscriptions in Angular components?
Ans: Use the takeUntil operator, async pipe, or a base component class to manage and clean up subscriptions.
85. Explain the purpose of the shareReplay operator in RxJS.
Ans: shareReplay shares a single subscription and replays a specified number of emitted values to new subscribers, optimizing resource use and avoiding multiple side effects.
Testing Advanced Scenarios
86. How do you test Angular components with async operations?
Ans: Use fakeAsync and tick for synchronous testing of async operations, or async and whenStable for handling real async operations in tests.
87. What is the purpose of the DebugElement in Angular testing?
Ans: DebugElement provides an abstraction over native DOM elements, allowing for querying, inspecting, and interacting with components in tests.
88. How do you mock services and HTTP calls in Angular tests?
Ans: Use libraries like Jasmine and Angular’s HttpClientTestingModule to create spies, mocks, and fake HTTP responses.
89. How do you test Angular directives?
Ans: Create a host component to apply the directive and test its behavior using DebugElement and query methods.
90. What are the best practices for writing maintainable Angular tests?
Ans: Best practices include isolating tests, using descriptive names, mocking dependencies, testing user interactions, and maintaining a clear separation between unit and integration tests.
Advanced Angular CLI
91. How do you create and use Angular CLI schematics?
Ans: Use @angular-devkit/schematics to create custom schematics, define rules, and integrate them with Angular CLI for code generation and modifications.
92. What are Angular CLI builders, and how do you customize them?
Ans: Builders are responsible for tasks like building, serving, and testing applications. Customize builders using angular.json or create custom builders with @angular-devkit/architect.
93. How do you use Angular CLI to generate libraries?
Ans: Use ng generate library to create a new library project within an Angular workspace, configure its ng-package.json, and build it using ng build.
94. What is the purpose of Angular CLI’s ng update command?
Ans: ng update updates Angular dependencies and applies necessary code transformations to keep projects up to date with the latest versions.
95. How do you use Angular CLI to enable differential loading?
Ans: Angular CLI automatically configures differential loading for modern and legacy browsers. Ensure browserslist is configured correctly in the project.
Advanced Deployment Techniques
96. How do you deploy an Angular application to AWS S3 and CloudFront?
Ans: Build the application with Angular CLI, upload the output to an S3 bucket, and configure CloudFront for CDN distribution and caching.
97. What are the steps to deploy an Angular application to Firebase Hosting?
Ans: Install Firebase CLI, initialize Firebase in the Angular project, build the application, and use firebase deploy to deploy it to Firebase Hosting.
98. How do you use Docker to containerize an Angular application?
Ans: Create a Dockerfile that builds and serves the Angular application using a base image like node or nginx, and use Docker Compose for multi-container setups.
99. What is server-side rendering (SSR), and how do you deploy an Angular Universal app?
Ans: SSR generates HTML on the server, improving performance and SEO. Build the Angular Universal app, deploy the server-side code to a Node.js server, and serve it using a hosting service like Heroku or AWS.
100. How do you implement continuous integration and continuous deployment (CI/CD) for Angular applications?
Ans: Use CI/CD tools like Jenkins, GitHub Actions, GitLab CI, or CircleCI to automate testing, building, and deployment processes for Angular applications. Configure pipelines to run tests, build artifacts, and deploy to staging or production environments.
