this is my code 

```html
<li v-for="(data, index) in datas" :key="data.id" class="nav-item">
  <a :href="#" :class="'nav-link '+ { 'active' : index === 0 }"  data-toggle="tab">
    {{data.name}}
  </a>
</li>

```

but output only showing like this

```html
<a href="#" data-toggle="tab" class="nav-link [object Object]">test</a>

```