function assignExtrasToUserData( object, gltfDef ) {

	if ( gltfDef.extras !== undefined ) {

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

			Object.assign( object.userData, gltfDef.extras );

		} else {

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

		}

	}

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