Angular Decorators and Metadata

Decorators are a part of TypeScript language, used to attach metadata to the classes, properties, and methods. Angular uses decorators extensively to add metadata to various components, services, directives, and pipes. These decorators help the Angular compiler to understand the source code and generate the appropriate JavaScript code for the browser.

Syntax

@DecoratorName({
  // metadata properties
})
export class ClassName {
  // class implementation
}

Example

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'My App';
}

Output

The above example is an Angular component that has been decorated with the @Component decorator and contains metadata properties like selector, templateUrl, and styleUrls. When the Angular compiler compiles this code, it generates the appropriate JavaScript code that will be served to the browser.

Explanation

Angular uses decorators extensively to attach metadata to various components, services, directives, and pipes. The metadata helps the Angular compiler to understand the source code and generate appropriate code for the browser.

Use

Some of the commonly used decorators in Angular are:

• @Component - attaches metadata to a component class
• @Injectable - attaches metadata to a service class
• @Directive - attaches metadata to a directive class
• @Pipe - attaches metadata to a pipe class
• @Input - attaches metadata to a component input property
• @Output - attaches metadata to a component output property

Important Points

• Decorators in Angular are used to attach metadata to various components, services, directives, and pipes.
• Metadata helps the Angular compiler to understand the source code and generate appropriate code for the browser.
• Angular provides many built-in decorators that can be used to attach metadata to different types of classes and properties.

Summary

Angular uses decorators extensively to attach metadata to various components, services, directives, and pipes. This metadata helps the Angular compiler understand the source code and generate the appropriate JavaScript code for the browser. By using decorators and metadata, Angular makes it easy to build complex applications with a smaller codebase.