CKQ/src/App.vue

<template>
  <div id="app" :class="theme+'-theme'">
    <router-view />
  </div>
</template>
<script>
export default {
  name: 'App',
  data() {
    return {
      theme: localStorage.getItem('theme') || 'default'
    }
  }
}
</script>