Layout.vue

<template>
  <nav>
    <a :class="isUrl('') ? 'active' : 'not-active'" href="/">Dashboard</a>
    <a :class="isUrl('users') ? 'active' : 'not-active'" href="/users">Users</a>
    <a :class="isUrl('reports') ? 'active' : 'not-active'" href="/reports">Reports</a>
  </nav>
</template>

<script>
export default {
  methods: {
    isUrl(...urls) {
      if (urls[0] === '') {
        return location.pathname.substr(1) === ''
      } else {
        return urls.filter(url => location.pathname.substr(1).startsWith(url)).length
      }
    },
  },
}
</script>