function assignExtrasToUserData(object, gltfDef) {

  if (gltfDef.extras !== undefined) {

    if (typeof gltfDef.extras === 'object') {

      object.userData = gltfDef.extras;

    } else {

      console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras);

    }

  }

}
@param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
@param {GLTF.definition} gltfDef