Get Properties of Object, but not of Parent Object

I have 2 Classes:

export class A extends B {
  private prop1: string;
  private prop2: string;
  constructor() {
    this.prop1 = "A";
    this.prop2 = "A";
  }
}

export abstract class B {
  private prop3: "B";
  constructor() {
    this.prop3 = "B";
  }
}

let a = new A();
let b = new B();

If I now do Object.getOwnProperties(a)
I also get the properties of the inherited class b.
–> prop1, prop2, prop3

Ist there any way to ONLY get prop1 and prop2, and omit prop3 as it is only an inherited property?

I know that Object.getOwnProperties(a) is the wrong approach, but is there any other approach I can go to ONLY get the properties of the baseClass, and not it`s inherited class also?