App.vue

<template>
  <!-- <div id="app" class="dark-theme white-theme"> -->
  <div id="app" :class="{'white-theme':theme=='white','dark-theme':theme=='dark'}">
    <router-view/>
  </div>
</template>

<script>
import {mapState} from 'vuex'
export default {
  name: 'App',
  data(){
    return {
      ctheme:'dark'
    }
  },
  computed:{
    ...mapState(['theme'])
  },
  watch: {
    theme(val){
      this.theme = val
      localStorage.setItem('theme',val)
    }
  },
}
</script>

<style>
#app {
  font-family: "微软雅黑",Arial,sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  color: #fff;
}
</style>