Fliped face orientation while fliping object

Hello, I’m trying to do “mirror effect”, but i want to keep normals. Any ideas how i could do this? Here’s my code (React):

useEffect(() => {
    const container: any = sceneRef.current!;
    scene.background = new THREE.Color("#D8D8D8");
    renderer.setSize(500, 500);
    container.appendChild(renderer.domElement);
    camera.position.z = -200;
    camera.position.y = 300;
    camera.position.x = 100;

    const controls = new OrbitControls(camera, renderer.domElement);
    controls.enableDamping = true;

    function animate() {
      requestAnimationFrame(animate);

      controls.update();

      renderer.render(scene, camera);
    }

    displayObject();

    animate();
    return () => {
      container.removeChild(renderer.domElement);
    };
  }, [objSrc, isRaf]);

const displayObject = () => {
    const light = new THREE.DirectionalLight(0xffffff, 1);
    const loader = new OBJLoader();
    loader.load(
      objSrc!,
      function (object: THREE.Group<THREE.Object3DEventMap>) {
        if (isRaf) {
          object.scale.x = -1;
        }
        scene.add(object);
        scene.add(light);
      }
    );
  };

const exportObj = () => {
    const exporter = new OBJExporter();
    const data = exporter.parse(scene);
    const blob = new Blob([data], { type: "text/plain" });
    const link = document.createElement("a");
    link.href = URL.createObjectURL(blob);
    const lafRaf = isRaf ? "RAF" : "Default_or_LAF_";
    link.download = `${
      lafRaf + "_" + (Math.random() * 1000000).toFixed(0)
    }.obj`;
    link.click();
  };

Maybe something like that ^ (untested)