VueJS exact-active-class

You can use v-if to check which route you're in and add class if $route.name is somewhere

<ul class="nav nav-second-level">
     <li v-for="item in menu" :class="{ 'IS-ACTIVATED': $route.name === somewhere }">
         <router-link :to="{ name: somewhere }">
             {{Name}}
         </router-link>
     </li>
 </ul>