What is Decorators in Angular5

What is Decorators in Angular 5

1. Decorators are a features of type Script and are implemented as functions. The name of the decorators starts with @ symbols following by brackets and arguments, Since decorators are just function in type Script.
2. Decorators are simply functions that return functions. These functions supply detadata to angular about a particular class, property, value or method.
3. Decorators are invoked at run-time.
4. Decorators allow you to execute functions. For example @Component executes the Component function imported from Angular 5.

Some Common Decorators

1. @NgModule() to define modules
2. @Compomnent() to define components
3. @Injectable() to define services
4. @Input() and @Output() to define properties that send and receive data from DOM
5. There are many built-in decorators available in angular and many properties on each decorators

Types of Decorators

1. Class Decorators – e.g. @Component and @NgModule
2. Property Decorators for properties inside class- e.g. @Input and @Output
3. Method Decorators for methods inside classes- e.g @HostListner
4. Parameter Decorators for parameters inside class constructors – e.g. @Inject
5. Each decorators has unique role.