Decorator
Decorators are functions, but a special kind of them. Decorators can used on classes, Methods, properties, and parameters. The best part is that you can write a decorator once and use it on many classes.
Example: Simplified Angular 2 component decorator
@Component({
template: '<h1>Hello this is {{title}}</h1>',
})
export class AppComponent {
title = 'My app!';
}
In the Above example AppComponent is a normal class with a title property, and it has a Component decorator above it. Because the Component decorator is above the class, it works with that class. Here it's defining a view for the AppComponent class, which data binds to the title property of the class. The Component decorator itself is a function.
You can write decorators yourself, as well. The function takes the object involved, the instance of the class it's above, and a configuration object as a parameter. It uses that information to do something with the object passed in.
We have got three basic type of decorator in typescript: