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Main Things to Know in Angular

Angular is a popular TypeScript-based web framework developed by Google for building client-side applications, primarily Single Page Applications (SPAs). To be proficient in Angular, here are the key concepts and features you should understand:

1. Core Architecture Concepts​

  • Modules: Organize functionality in Angular. Every app has at least one root module (AppModule). Larger apps use feature modules and lazy loading for better organization.
  • Components: Building blocks that define views and behavior. A component consists of:
    • HTML template: Defines the UI.
    • TypeScript class: Contains logic and state.
    • CSS styles: Scoped styles for the component.
  • Services: Reusable logic (e.g., data fetching, logging). Injected using Dependency Injection (DI).
  • Directives: Instructions for manipulating the DOM:
    • Structural Directives: (*ngIf, *ngFor) modify DOM structure.
    • Attribute Directives: (ngClass, ngStyle) change appearance or behavior.
  • Pipes: Transform data in templates (e.g., date, uppercase). Custom pipes can also be created.

2. Data Binding​

Angular offers different ways to bind data between the template and the component:

  • Interpolation: {{ expression }} displays component data in the view.
  • Property Binding: [property]="expression" binds component values to HTML element properties.
  • Event Binding: (event)="handlerMethod()" binds DOM events to component methods.
  • Two-Way Binding: [(ngModel)]="property" synchronizes data between the view and the component.

3. Routing​

Angular’s router handles navigation in SPAs:

  • Router Module: Defines routes that map to components.
  • RouterLink: <a [routerLink]="['/path']"> for navigation.
  • Route Guards: Control access to routes (e.g., CanActivate).
  • Lazy Loading: Load feature modules only when needed to improve performance.

4. Forms Handling​

Angular supports two types of forms:

  • Template-driven Forms: Use ngModel for simple forms.
  • Reactive Forms: Manage forms programmatically in the component, offering more flexibility for dynamic validation and form control.

5. Dependency Injection (DI)​

Angular’s DI system allows you to inject services or dependencies into components, services, or other classes, ensuring modularity and testability. The DI system is hierarchical.

6. RxJS and Observables​

Angular uses RxJS for reactive programming and handling asynchronous events, especially in:

  • HTTP requests (via HttpClient).
  • Event handling.
  • Data streams. You’ll need to understand RxJS operators (map(), filter(), etc.) and how to work with Observables (subscribe(), pipe()).

7. HTTP Client​

Angular's HttpClient is used for making HTTP requests:

  • Supports standard HTTP methods (GET, POST, etc.).
  • Returns Observables for asynchronous operations.
  • Use interceptors for adding headers (e.g., authentication tokens) or handling errors globally.

8. State Management​

Managing state across components can be challenging:

  • NgRx: A Redux-inspired library for managing application state in Angular.
  • Service-based state management: Using services with RxJS Subject or BehaviorSubject for simpler state sharing between components.

9. Testing​

Angular provides built-in tools for testing:

  • Unit Testing: Use Jasmine and Karma for testing components, services, and other units.
  • End-to-End (e2e) Testing: Use Protractor for simulating user interactions and testing the app's functionality as a whole.

10. Performance Optimization​

  • Ahead-of-Time (AOT) Compilation: Compiles templates at build time to reduce bundle sizes and improve performance.
  • Lazy Loading: Load modules only when necessary.
  • Change Detection: Use efficient change detection strategies like OnPush or trackBy in ngFor to reduce performance overhead.
  • Tree Shaking: Removes unused code during the build process.

11. Angular CLI​

Angular CLI is a command-line tool that simplifies development. Key commands:

  • ng serve: Runs the app locally.
  • ng generate: Generates components, services, etc.
  • ng build: Compiles the app for production.
  • ng test: Runs unit tests.

12. Best Practices​

  • Follow Angular Style Guide: Helps maintain consistency and best practices.
  • Modular Design: Use feature modules to manage complexity.
  • RxJS Best Practices: Handle subscriptions properly to avoid memory leaks.
  • Security: Implement XSS and CSRF protection, use Angular's built-in data sanitization.

Summary​

To summarize, the main things to know in Angular are:

  • Core building blocks: Components, modules, services, directives, pipes.
  • Routing: For navigation and lazy loading.
  • Forms: Template-driven and reactive forms for handling user input.
  • Dependency Injection: For injecting services and dependencies.
  • RxJS: Understanding Observables for handling asynchronous tasks.
  • HTTP Client: For making HTTP requests and handling APIs.
  • Testing: Unit and end-to-end testing to ensure app quality.
  • Performance: Optimize for performance with AOT, lazy loading, and efficient change detection.
  • State Management: Using NgRx or services to handle shared state.
  • CLI: For building, testing, and running the app.

Understanding these concepts will help you build robust and scalable Angular applications.