vue +elementui 项目登录通过不同账号切换侧边栏菜单的颜色

// 主要是切换菜单栏和菜单头部主题的设计，整体主题样式切换是否能匹配
export const _Theme = {
  'lightTheme': {
    // 默认主题样式，要和varibles.scss的变量参数属性一样，theme为1
    menuBg: '#ffffff',
    menuText: '#464646',
    subMenuActiveText: '#464646',
    menu: '#F7FCFF'
  },
  'darkTheme': {
    // 深色主题，theme为2
    menuBg: '#2781AB',
    menuText: '#BDCBD9',
    subMenuActiveText: '#ffffff',
    menu: '#106E9A'
  }
}

<template>
  <div id="app">
    <router-view />
  </div>
</template>
<script>
import { _Theme } from './theme.js'
export default {
  name: 'App',
  computed: {
    nowTheme: {
      get() {
        return this.$store.state.user.user.theme
      }
    }
  },
  watch: {
    // 主题切换
    nowTheme() {
      if (this.nowTheme === 2) {
        this.changeStyle(_Theme.darkTheme)
      } else {
        this.changeStyle(_Theme.lightTheme)
      }
    }
  },
  methods: {
  //主要代码
    changeStyle(obj) {
      for (const key in obj) {
        document.getElementsByTagName('body')[0].style.setProperty(`--${key}`, obj[key])
      }
    }
  }
}
</script>
侧边栏文件：index.vue:
```javascript
<template>
    <el-scrollbar wrap-class="scrollbar-wrapper">
      <el-menu
        :default-active="activeMenu"
        :collapse="isCollapse"
        :background-color="variablesa.menuBg"
        :text-color="variablesa.menuText"
        :unique-opened="$store.state.settings.uniqueOpened"
        :active-text-color="variablesa.menuActiveText"
        :collapse-transition="false"
        mode="vertical"
      >
        <sidebar-item
          v-for="route in sidebarRouters"
          :key="route.path"
          :item="route"
          :base-path="route.path"
        />
      </el-menu>
    </el-scrollbar>
</template>
<script>
import SidebarItem from './SidebarItem'
import variables from '@/assets/styles/variables.scss' //主要代码
export default {
  computed: {
    variablesa() {
      return variables
    }
  }
}
</script>

// sidebar
$menuText:var(--menuText,#464646);
$menuActiveText:var(--menuActiveText,$--color-theme);
$subMenuActiveText:var(--subMenuActiveText,#464646);
$menuBg:var(--menuBg,#ffffff);//侧边栏菜单主题色
$menuTopBg:transparent;//顶栏菜单主题色
$menuHover:var(--menu,#F7FCFF);
$subMenuBg:var(--menu,#F7FCFF);
$subMenuHover:var(--menu,#F7FCFF);
$sideBarWidth: 260px;
:export {
  menuText: $menuText;
  menuActiveText: $menuActiveText;
  subMenuActiveText: $subMenuActiveText;
  menuBg: $menuBg;
  menuTopBg: $menuTopBg;
  menuHover: $menuHover;
  subMenuBg: $subMenuBg;
  subMenuHover: $subMenuHover;
  sideBarWidth: $sideBarWidth;
}