webpack - Vue with webkit - Unexpected token punc «(», expected punc «:» -

i have error when trying uglify vuejs project

 unexpected token punc «(», expected punc «:» 

it when trying export component nav.vue

export default {   props: ['pagename'],   data () {     return {       activenav:0     }   }, 

it not seem data() syntax. has solved this?

i did not have .babelrc file

{   "presets": [     "es2015"   ]  }