Implement simple dependency injection with Reflect

dependency-injection.ts

const reflectObj = {};

function Injectable() {
  return function (target: any) {
    console.log('Injectable');
    Reflect.defineMetadata('injectable', true, target);
    reflectObj[target] = true;
  };
}

@Injectable()
class MyDependency {
  doSomething() {
    console.log('MyDependency is doing somethingggggggggggggggggggggggggggg');
  }
}

@Injectable()
class MyService {
  constructor(private myDependency: MyDependency) {}

  doSomething() {
    this.myDependency.doSomething();
  }
}

class DependencyInjection {
  static get<T>(target: any): T {
    const isInjectable = Reflect.getMetadata('injectable', target);
    const isInjectable2 = reflectObj[target];
    console.log('isInjectablee', isInjectable, isInjectable2);

    if (!isInjectable2) {
      return;
      // throw new Error('Target is not injectable');
    }

    const dependencies = Reflect.getMetadata('design:paramtypes', target) || [];
    console.log(dependencies, dependencies.length);
    const instances = dependencies.map((dep) => DependencyInjection.get(dep));
    return new target(...instances);
  }
}

const myService = DependencyInjection.get<MyService>(MyService);
console.log('myServiceeeeeee:', myService.doSomething());