multipart element ui

<form name="documentForm" ref="form" @submit.prevent = "store$" method="post" enctype="multipart/form-data">

<el-upload        :on-change="handleChange"        :file-list="create$.file"        action=""        class="upload-demo"        ref="upload"        multiple        :auto-upload="false">
    <v-btn slot="trigger">Upload</v-btn>
</el-upload>

<v-btn color="blue darken-1" flat form="documentForm" type="submit">Save</v-btn>

</form>
new Vue({
methods:{
store$(){
    var vm = this    var store$ = new FormData(vm.$refs.form);    store$.append('category_id', vm.create$.category_id )
    _.map(vm.create$.file, function(data){
        store$.append('file[]', data.raw )
    })


    post('/api/documents', store$).then(function (response) {
        vm.$set(vm.$root.$data.documents, vm.$root.$data.documents.length, response.data )
        vm.$root.successResponse('Create A Document')
        vm.$router.push('/documents')
    }).catch(function (_ref2) {
        vm.$root.errorResponse(_ref2)
    });

}
})