Questions and Answers
What is a key feature of standalone components in Angular?
Which of the following operators is used to transform emitted items in RxJS?
What do structural directives do in Angular?
In RxJS, which operator combines the latest values from multiple observables?
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What is the role of the @Directive decorator in Angular?
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What is a core feature of Angular components?
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Which decorator is used to define an Angular service?
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What is the role of Route Guards in Angular Routing?
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What is an advantage of using Dependency Injection in Angular?
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What is the purpose of state management in Angular applications?
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Which state management library is commonly used in Angular applications?
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What does the OnPush change detection strategy do in Angular?
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Which service scope provides services that are unique to specific components in Angular?
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Study Notes
Angular Framework Study Notes
Components
- Definition: Reusable building blocks of an Angular application.
- Structure: Composed of a TypeScript class, an HTML template, and CSS styles.
- Lifecycle Hooks: Include ngOnInit, ngOnChanges, ngOnDestroy, etc., which allow developers to tap into key moments in a component's lifecycle.
Services
- Purpose: Reusable business logic and data fetching, separate from UI components.
- Creation: Defined using the @Injectable() decorator.
- Usage: Can be injected into components or other services.
Routing
- Routing Module: Manages navigation between different components.
- Router Configuration: Defines routes with path, component, and optional guards.
- RouterLink: Directive used for navigation.
- Route Guards: Interfaces to protect routes (canActivate, canDeactivate, etc.).
Dependency Injection
- Concept: A design pattern used to manage service instances.
- Providers: Declare how to create instances of services.
- Injectors: Hierarchical structure that maintains instances of services.
State Management
- Purpose: Manages the state of an application effectively.
- Libraries: Popular choices include NgRx and Akita.
- State: Represents the data model of the application, often kept in a centralized store.
Change Detection
- Mechanism: Angular's way of tracking changes in the application model and updating the view.
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Strategies:
- Default: Checks all components.
- OnPush: Only checks components with changed inputs or events.
- Zone.js: Library that helps Angular detect changes automatically.
Service Scopes
- Root Scope: Services provided once, shared across the application.
- Component Scope: Services provided in a component, unique to that component instance.
- Module Scope: Services available to all components within a specific module.
Directives
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Types:
- Structural Directives: Alter the DOM structure (e.g., *ngIf, *ngFor).
- Attribute Directives: Change the appearance or behavior of elements (e.g., ngClass, ngStyle).
- Creation: Defined using the @Directive decorator.
RxJs Operators
- Purpose: Facilitate asynchronous programming and handling streams of data.
-
Common Operators:
- map: Transforms emitted items.
- filter: Emits items that pass a condition.
- mergeMap: Flattens higher-order Observables.
- combineLatest: Combines the latest values from multiple Observables.
Standalone Components
- Concept: Components that do not require a module to be declared or used.
- Usage: Allows for simpler architecture and reduced boilerplate code.
- Decorator: Identified by the @Component decorator with the standalone property set to true.
Components
- Reusable building blocks that define the UI and behaviors of an Angular application.
- Consist of a TypeScript class for logic, an HTML template for structure, and CSS for styling.
- Lifecycle hooks like ngOnInit, ngOnChanges, and ngOnDestroy enable interaction at important stages of the component lifecycle.
Services
- Serve as a means to encapsulate business logic and manage data fetching away from UI components.
- Created using the @Injectable() decorator, indicating that the service can be injected into other classes.
- Can be implemented in components or other services for improved modularity and code reuse.
Routing
- Manages navigation between different views or components in an Angular application via a Router Module.
- Configured by defining routes that associate paths with specific components, alongside optional route guards for security.
- The RouterLink directive provides a way to create navigation links in templates.
- Route guards (canActivate, canDeactivate) define conditions for allowing or preventing access to routes.
Dependency Injection
- Essential design pattern in Angular for managing instances of services, promoting loose coupling.
- Providers establish how services are created and instantiated, enabling easier management.
- Injectors form a hierarchical structure that controls which services are available and their lifetimes.
State Management
- Deals with effective state handling for Angular applications, ensuring smooth data flow.
- Libraries such as NgRx and Akita are popular for maintaining state in a centralized store.
- The application’s state reflects its data model, improving performance and data consistency.
Change Detection
- Mechanism used to identify and respond to changes in the application’s model, updating the view accordingly.
- Features change detection strategies like Default (checks all components) and OnPush (checks only those with changed inputs).
- Zone.js is utilized to enable automatic detection of changes, enhancing performance.
Service Scopes
- Root Scope: Services are provided once and shared globally throughout the application.
- Component Scope: Services are unique to the instance of the component in which they are provided.
- Module Scope: Services are accessible to all components within a specific module, allowing for organized service management.
Directives
- Structural Directives modify the DOM structure, allowing for dynamic content rendering (*ngIf, *ngFor).
- Attribute Directives alter the appearance or behavior of existing elements (ngClass, ngStyle).
- Created using the @Directive decorator for custom behavior within Angular templates.
RxJs Operators
- Designed to enhance asynchronous programming and facilitate stream handling within Angular applications.
- Common operators include:
- map: Transforms data emitted by observables.
- filter: Emits only those items that meet specified conditions.
- mergeMap: Flattens observables for easier data manipulation.
- combineLatest: Gathers the most recent values from multiple observables for synchronized updates.
Standalone Components
- Define components that do not require a module for declaration or usage, streamlining architecture.
- Promote simpler designs and reduce boilerplate code, improving development efficiency.
- Identified through the @Component decorator, featuring a standalone property set to true.
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Description
This quiz covers key concepts of the Angular framework, including components, services, routing, and dependency injection. Test your understanding of how these fundamental building blocks contribute to Angular application development.
