dynamic validations - manually clear validators and set validators

delivery-page.component.ts

    this.subscription.add(
      this.deliveryPageForm.get('isShippingSame').valueChanges.subscribe((isShippingSame: boolean) => {
        if (isShippingSame) {
          this.deliveryPageForm.get('shippingAddress').reset();
          this.deliveryPageForm.get('shippingAddress').clearValidators();
        } else {
          this.deliveryPageForm.get('shippingAddress').setValidators([Validators.required]);
        }
      })
    );

    this.subscription.add(
      this.deliveryPageForm.get('createAccount').valueChanges.subscribe((createAccount: boolean) => {
        if (createAccount) {
          this.deliveryPageForm.get(['account', 'password']).setValidators([Validators.required]);
          this.deliveryPageForm.get(['account', 'confirmPassword']).setValidators([Validators.required]);
          this.deliveryPageForm.get(['account', 'password']).reset();
          this.deliveryPageForm.get(['account', 'confirmPassword']).reset();
        } else {
          this.deliveryPageForm.get(['account', 'password']).clearValidators();
          this.deliveryPageForm.get(['account', 'confirmPassword']).clearValidators();
        }
      })
    );