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I just started using Angular 2 and was wondering why some properties like selector and template are put in components decorators and not in components classes.
What's the point of using all these decorators in Angular 2?
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The whole purpose of Angular decorators is to store metadata about a class, method, or property. When you configure a component, you are providing a metadata for that class that tells Angular that you have a component, and that component has a specific configuration.
Decorators provide a way to add both annotations and a meta-programming syntax for class declarations and members. Decorators are a stage 2 proposal for JavaScript and are available as an experimental feature of TypeScript. NOTE Decorators are an experimental feature that may change in future releases.
Annotations are only metadata set on the class using the Reflect Metadata library. Decorator corresponds to a function that is called on the class. Annotations are used for creating an attribute annotations that stores array. Decorator is a function that gets the object that needs to be decorated.
Decorators are design patterns used to isolate the modification or decoration of a class without modifying the source code. In AngularJS, decorators are functions that allow a service, directive, or filter to be modified before it is used.
To make it easy for tools to provide all kinds of support in templates like:
To generate code from decorators which allows:
Code would need to be executed to use results expressions might emit. Decorators can be easily evaluated statically without executing the TypeScript code (except maybe a simple and limited subset).
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