TS - decorator depends on another regardless of their place in class

Question

Could we run a function decorator @A systematically before @B regardless of their place in the class?

class Exemple {

@A()
public method1(): void { ... }

@B()
public method2(): void { ... }

@A()
public method3(): void { ... }

}

Above, I would like @A of method1 and method3 to run before @B() regardless of the place of the method in the class.

Answer 1

I found a trick with ReflectMetadata:

A decorator

export const A =
  () =>
  (consumer: any, methodName: string, descriptor: PropertyDescriptor) => {
    const existingAMethods =
      Reflect.getOwnMetadata("A_METHODS", consumer.constructor) || []
    const options: {
      consumer,
      methodName,
      descriptor
    }
    existingAMethods.push(options)
    Reflect.defineMetadata(
      "A_METHODS",
      existingAMethods,
      consumer.constructor
    )
  }

B decorator

export const B =
  () =>
  (consumer: any, methodName: string, descriptor: PropertyDescriptor) => {
    const existingBMethods =
      Reflect.getOwnMetadata("B_METHODS", consumer.constructor) || []
    const options: {
      consumer,
      methodName,
      descriptor
    }
    existingBMethods.push(options)
    Reflect.defineMetadata(
      "B_METHODS",
      existingBMethods,
      consumer.constructor
    )
  }

and a last one "C"

export const C = () =>
  (constructor: Function): void => {
    const options =
      Reflect.getOwnMetadata("A_METHODS", constructor) || []
    // DO some actions relatecd to A
    const options =
      Reflect.getOwnMetadata("B_METHODS", constructor) || []
    // DO some actions relatecd to B
  }

usage

@C()
class Exemple {

  @A()
  public method1(): void { ... }

  @B()
  public method2(): void { ... }

  @A()
  public method3(): void { ... }

}