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} def