Q1. What is Angular?
Answer
Angular is a platform and framework for building single-page client applications using HTML and TypeScript. It is developed and maintained by Google and provides a comprehensive solution for creating dynamic web applications.
Q2. What are the key differences between AngularJS and Angular?
Answer
AngularJS is based on JavaScript and uses the MVC (Model-View-Controller) architecture, while Angular is built with TypeScript and uses a component-based architecture. Angular also introduces features like improved dependency injection, a more powerful templating system, and better performance optimizations.
Q3. What is a component in Angular?
Answer
A component is a fundamental building block of Angular applications. It encapsulates the HTML template, styles, and logic (TypeScript code) for a specific part of the UI. Components are defined using the '@Component' decorator.
Q4. What are directives in Angular?
Answer
Directives are classes that add additional behavior to elements in your Angular applications. There are three types of directives: component directives, structural directives (e.g., 'ngIf', 'ngFor'), and attribute directives (e.g., 'ngStyle', 'ngClass').
Q5. What is the purpose of the 'ngOnInit' lifecycle hook?
Answer
The 'ngOnInit' lifecycle hook is called once after the component's properties are initialized. It is commonly used to perform initialization tasks such as fetching data from a server.
Q6. What is dependency injection in Angular?
Answer
Dependency injection is a design pattern that allows a class to receive its dependencies from an external source rather than creating them itself. In Angular, dependency injection is managed by the injector, which provides instances of dependencies as needed.
Q7. What are services in Angular?
Answer
Services in Angular are singleton objects that provide specific functionality to components, such as data retrieval or business logic. They are created using the '@Injectable' decorator and can be injected into components or other services using dependency injection.
Q8. What is the purpose of Angular modules?
Answer
Angular modules help organize an application into cohesive blocks of functionality. A module is a class decorated with the '@NgModule' decorator, which defines metadata such as declarations, imports, exports, providers, and bootstrap components.
Q9. What is the 'angular.json' file used for?
Answer
The 'angular.json' file stores all the configurations of the Angular application. It tells the builder the entry point of the application and creates a browser environment for the application to run.
Q10. What is Ahead-of-Time (AOT) compilation?
Answer
AOT compilation converts Angular HTML and TypeScript code into efficient JavaScript code during the build process, rather than at runtime. This results in faster rendering times, smaller bundle sizes, and improved security.
Q11. What are Angular pipes?
Answer
Pipes are used to transform data before displaying it in the UI. Angular provides built-in pipes like 'DatePipe', 'UpperCasePipe', and 'LowerCasePipe', and you can also create custom pipes.
Q12. What is the purpose of the 'ngModel' directive?
Answer
The 'ngModel' directive is used for two-way data binding between a form control and a component property. It allows for automatic synchronization of data between the view and the model.
Q13. What are Angular forms and what are the differences between template-driven and reactive forms?
Answer
Angular forms are used to handle user input. Template-driven forms rely on Angular directives in the template to manage form state and validation, while reactive forms use a more programmatic approach with RxJS and form control instances in the component class.
Q14. What is the purpose of the 'HttpClient' module?
Answer
The 'HttpClient' module is used to make HTTP requests to a server. It provides a simplified API for sending GET, POST, PUT, DELETE, and other types of requests, and handling responses.
Q15. What are Angular routes and how do you define them?
Answer
Angular routes are used to navigate between different views in an application. Routes are defined using the 'RouterModule' and the '@NgModule' decorator, and they map URLs to components.
Q16. What is lazy loading in Angular?
Answer
Lazy loading is a technique used to load modules on demand, rather than at the initial load of the application. This improves performance by reducing the initial load time and only loading modules when they are needed.
Q17. What are Angular guards and what are their types?
Answer
Guards are used to control access to routes. There are several types of guards, including 'CanActivate', 'CanDeactivate', 'Resolve', 'CanLoad', and 'CanActivateChild'. They help protect routes based on certain conditions, such as user authentication or data resolution.
Q18. What is the purpose of the 'ngIf' directive?
Answer
The 'ngIf' directive is used to conditionally include or exclude an element from the DOM based on a boolean expression. It is a structural directive that adds or removes elements based on the condition.
Q19. What is the purpose of the 'ngFor' directive?
Answer
The 'ngFor' directive is used to repeat a template for each item in a list. It is a structural directive that iterates over an array or iterable and creates a template instance for each item.
Q20. What are Angular decorators?
Answer
Decorators are a design pattern in Angular that allows you to modify or extend the behavior of classes, methods, properties, or parameters. Common decorators include '@Component', '@NgModule', '@Injectable', and '@Input'.
Q21. What is the purpose of the 'ngOnChanges' lifecycle hook?
Answer
The 'ngOnChanges' lifecycle hook is called whenever an input property of a component changes. It is used to respond to changes in input properties and update the component's state accordingly.
Q22. What is the purpose of the 'ngDoCheck' lifecycle hook?
Answer
The 'ngDoCheck' lifecycle hook is called during every change detection run. It is used to perform custom change detection logic that cannot be handled by Angular's default change detection strategy.
Q23. What is the purpose of the 'ngAfterViewInit' lifecycle hook?
Answer
The 'ngAfterViewInit' lifecycle hook is called after Angular has fully initialized a component's views. It is used to perform initialization tasks that require the view to be fully initialized.
Q24. What is the purpose of the 'ngOnDestroy' lifecycle hook?
Answer
The 'ngOnDestroy' lifecycle hook is called just before a component is destroyed. It is used to perform cleanup tasks, such as unsubscribing from observables or releasing resources.
Q25. What is the purpose of the 'ngAfterContentInit' lifecycle hook?
Answer
The 'ngAfterContentInit' lifecycle hook is called after Angular has fully initialized a component's content. It is used to perform initialization tasks that require the content to be fully initialized.
Q26. What is the purpose of the 'ngAfterContentChecked' lifecycle hook?
Answer
The 'ngAfterContentChecked' lifecycle hook is called after Angular has checked the content of a component. It is used to perform tasks that require the content to be up-to-date.
Q27. What is the purpose of the 'ngAfterViewChecked' lifecycle hook?
Answer
The 'ngAfterViewChecked' lifecycle hook is called after Angular has checked the view of a component. It is used to perform tasks that require the view to be up-to-date.
Q28. What is the purpose of the 'ngOnInit' lifecycle hook?
Answer
The 'ngOnInit' lifecycle hook is called once after the component's properties are initialized. It is commonly used to perform initialization tasks such as fetching data from a server.
Q29. What is the purpose of the 'ngOnChanges' lifecycle hook?
Answer
The 'ngOnChanges' lifecycle hook is called whenever an input property of a component changes. It is used to respond to changes in input properties and update the component's state accordingly.
Q30. What is the purpose of the 'ngDoCheck' lifecycle hook?
Answer
The 'ngDoCheck' lifecycle hook is called during every change detection run. It is used to perform custom change detection logic that cannot be handled by Angular's default change detection strategy.
Q31. What is NgRx and how is it used in Angular?
Answer
NgRx is a state management library for Angular applications. It provides a centralized store for application state, along with actions, reducers, and effects to manage state changes. NgRx helps manage state in a predictable and maintainable way.
Q32. What are the benefits of using NgRx for state management?
Answer
NgRx offers several benefits, including a centralized store for application state, predictable state management, and integration with RxJS for reactive programming. It also provides tools for debugging and monitoring state changes.
Q33. What are Angular effects in NgRx?
Answer
Effects in NgRx are used to handle side effects, such as making HTTP requests or interacting with external APIs. They listen for actions and perform asynchronous operations, dispatching new actions based on the results.
Q34. What are Angular reducers in NgRx?
Answer
Reducers in NgRx are pure functions that take the current state and an action as arguments and return a new state. They define how the application's state changes in response to actions.
Q35. What are Angular actions in NgRx?
Answer
Actions in NgRx are plain JavaScript objects that describe a unique event that occurs in the application. They are dispatched to the store to trigger state changes and are handled by reducers.
Q36. What is change detection in Angular?
Answer
Change detection is the process by which Angular updates the DOM in response to changes in the application's state. Angular uses a change detection strategy to determine when and how to update the view.
Q37. What is the OnPush change detection strategy?
Answer
The OnPush change detection strategy is used to optimize performance by limiting the frequency of change detection cycles. It is activated by setting the 'changeDetection' property to 'ChangeDetectionStrategy.OnPush' in a component's metadata.
Q38. What are the benefits of lazy loading in Angular?
Answer
Lazy loading improves performance by reducing the initial load time of the application and only loading modules when they are needed. This results in faster load times and a better user experience.
Q39. What is Ahead-of-Time (AOT) compilation and why is it important?
Answer
AOT compilation converts Angular HTML and TypeScript code into efficient JavaScript code during the build process, rather than at runtime. This results in faster rendering times, smaller bundle sizes, and improved security.
Q40. What are some techniques for optimizing the performance of an Angular application?
Answer
Techniques for optimizing performance include lazy loading modules, using the OnPush change detection strategy, reducing bundle size through tree-shaking and minification, and leveraging AOT compilation. Additionally, optimizing HTTP requests and using efficient data structures can improve performance.
Q41. What is the purpose of Angular's TestBed?
Answer
TestBed is a core class in Angular's testing utilities that provides a testing environment for components and services. It allows developers to configure modules, providers, and other dependencies needed for tests.
Q42. What are the different types of tests in Angular?
Answer
The different types of tests in Angular include unit tests, integration tests, and end-to-end (E2E) tests. Unit tests focus on individual components or services, integration tests verify the interaction between multiple components, and E2E tests simulate user interactions with the application.
Q43. What tools are commonly used for testing in Angular?
Answer
Common tools for testing in Angular include Jasmine and Karma for unit tests, and Protractor for E2E tests. These tools provide a framework for writing and running tests, as well as asserting expectations.
Q44. What is the purpose of the 'ng test' command?
Answer
The 'ng test' command is used to run unit tests in an Angular application. It uses the Karma test runner to execute tests and provides feedback on test results.
Q45. What is the purpose of the 'ng e2e' command?
Answer
The 'ng e2e' command is used to run end-to-end tests in an Angular application. It uses the Protractor test runner to simulate user interactions and verify the application's behavior.
Q46. What are some best practices for structuring an Angular project?
Answer
Best practices for structuring an Angular project include using feature modules to group related components, services, and other artifacts, and adopting a consistent naming convention for files and folders. Keeping the app module lean and delegating responsibilities to feature modules promotes separation of concerns and improves maintainability.
Q47. What are some best practices for handling forms in Angular?
Answer
Best practices for handling forms in Angular include using reactive forms for complex form scenarios, validating form inputs using built-in and custom validators, and providing clear error messages to users. Additionally, using form control instances to manage form state and validation helps maintain a clean and maintainable codebase.
Q48. What are some best practices for managing state in Angular?
Answer
Best practices for managing state in Angular include using services to share state between components, leveraging RxJS for reactive state management, and employing state management libraries like NgRx for complex state scenarios. Keeping state management centralized and predictable helps maintain a consistent and responsive application.
Q49. What are some best practices for optimizing the performance of an Angular application?
Answer
Best practices for optimizing performance include lazy loading modules, using the OnPush change detection strategy, reducing bundle size through tree-shaking and minification, and leveraging AOT compilation. Additionally, optimizing HTTP requests and using efficient data structures can improve performance.
Q50. What are some best practices for testing in Angular?
Answer
Best practices for testing in Angular include writing unit tests for individual components and services, using integration tests to verify the interaction between multiple components, and employing end-to-end tests to simulate user interactions. Using tools like Jasmine, Karma, and Protractor, and following the TestBed configuration for tests, helps ensure comprehensive test coverage and maintainable test suites.
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