Decorator example

decorator.ts

export default function showMessage(message: string) {
  console.log('message', message);

  return (...args: any[]) => {
    const [constructorOrComponent, propertyKey, descriptor] = args;

    if (typeof constructorOrComponent === 'function') {
      console.log('Class', constructorOrComponent);
      return constructorOrComponent;
    }

    if (!descriptor) {
      console.log('Prop', constructorOrComponent, propertyKey);
      return undefined;
    }

    console.log('Class method', constructorOrComponent, propertyKey, descriptor);
    return descriptor;
  };
}