Decorator in Angular 7

->Decorators are a feature of TypeScript and are implemented as functions.

The name of the decorator starts with @symbol following by brackets and arguments,since decorators are just functions in TypeScript .

->Decorators are simply functions that return functions. These functions supply metadata to Angular about a particular class, property, value, or method.

->Decorators are invoked at runtime.

->Decorators allow you to executes functions. For example @Component executes the Component function imported  from Angular7

Some Common Decorators

@NgModule() to define modules.

@Component() to define components.

@Injectable() to define services.

@Input() and @Output() to define properties ..that send and receive data from the dome.

There are many built-in decorators available in Angular and many properties on each decorator.

Types Of Decorators

->Class decorators. e.g. @Component and @NgModule

->Property decorators for properties inside classes,

e.g. @Input and @Output

->Method decorators for methods inside classes, e.g @HostListener

->Parameter decorators for parameters inside class constructors e.g. @Inject

Each decorator has a unique role.