路由元信息（Route Meta Information）是在路由配置中为每个路由定义的一组自定义数据。这些数据可以包含任何你希望在路由中传递和使用的信息，比如权限、页面标题、布局设置等。Vue Router 允许你在路由配置中定义元信息，然后在组件中访问这些信息。

在 Vue Router 中，你可以通过 meta 字段来定义路由的元信息。下面是一个定义title的示例：

index.ts

import { createRouter, createWebHistory } from 'vue-router'

declare module 'vue-router' {
  interface RouteMeta {
    title: string
  }
}

export const router = createRouter({
  // import.meta.env.BASE_URL 应用的基本 URL。基本 URL 是指在你的应用部署到某个域名或子路径时，URL 的起始部分。例如，如果你的应用部署在 https://example.com/myapp/ 这个路径下，那么 import.meta.env.BASE_URL 就会是 /myapp/。
  history: createWebHistory(import.meta.env.BASE_URL),
  routes: [
    {
      path: '/',
      component: () => import('@/views/Login.vue'),
      meta: {
        title: "登录页",
      }
    },
    {
      path: '/index',
      component: () => import('@/views/Index.vue'),
      meta: {
        title: "首页",
      }
    },
  ],
})

loadingBar.vue

<template>
  <div class="wraps">
    <div ref="bar" class="bar"></div>
  </div>
</template>

<script setup lang="ts">
import { ref, onMounted } from 'vue'
let speed = ref<number>(1)
let bar = ref<HTMLElement>()
let timer = ref<number>(0)
const startLoading = () => {
  speed.value = 1
  let dom = bar.value as HTMLElement
  timer.value = window.requestAnimationFrame(function fn() {
    if (speed.value < 90) {
      speed.value += 1;
      dom.style.width = speed.value + '%'
      timer.value = window.requestAnimationFrame(fn)
    } else {
      speed.value = 1
      window.cancelAnimationFrame(timer.value)
    }
  })
}
const endLoading = () => {
  let dom = bar.value as HTMLElement
  setTimeout(() => {
    window.requestAnimationFrame(() => {
      speed.value = 100
      dom.style.width = speed.value + '%'
    })
  }, 500)

}

defineExpose({ startLoading, endLoading })
</script>

<style scoped lang="less">
.wraps {
  width: 100%;
  position: fixed;
  height: 10px;
  top: 0;

  .bar {
    height: inherit;
    width: 0;
    background-color: #409eff;
  }
}
</style>

Index.vue

<template>
  <h1>
    我进来啦
  </h1>
</template>

<script setup lang="ts">

</script>

<style scoped></style>

Login.vue

<template>
  <div class="login">
    <el-card class="box-card">
      <el-form ref="form" :rules="rules" :model="formInline" class="demo-form-inline">
        <el-form-item prop="user" label="账号：">
          <el-input v-model="formInline.user" placeholder="请输入账号" />
        </el-form-item>
        <el-form-item prop="password" label="密码：">
          <el-input v-model="formInline.password" placeholder="请输入密码" type="password"></el-input>
        </el-form-item>
        <el-form-item>
          <el-button type="primary" @click="onSubmit">登录</el-button>
        </el-form-item>
      </el-form>
    </el-card>
  </div>
</template>

<script setup lang="ts">
import { reactive, ref } from 'vue'
import { useRouter } from 'vue-router'
import type { FormItemRule, FormInstance } from 'element-plus';
import { ElMessage } from 'element-plus'

const router = useRouter()
type Form = {
  user: string,
  password: string
}
type  Rules = {
  [k in keyof Form]?: Array<FormItemRule>
}
const formInline = reactive<Form>({
  user: '',
  password: '',
})
const form = ref<FormInstance>()
const rules = reactive({
  user: [
    {
      required: true,
      message: '请输入账号',
      type: 'string',
    }
  ],
  password: [
    {
      required: true,
      message: '请输入密码',
      type: 'string',
    }
  ]
})

const onSubmit = () => {
  console.log('submit!', form.value)
  form.value?.validate((validate)=>{
    if (validate) {
      router.push('/index')
      localStorage.setItem('token', '1')
    } else {
      ElMessage.error('账号或密码错误')
    }
  })

}
</script>

<style scoped lang="less">
.login {
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
}
</style>

App.vue

<template>
  <router-view></router-view>
</template>

<script setup lang="ts">


</script>

<style>
/* 注意 style 标签 别加 scoped 不然设置宽高不生效 */
* {
  margin: 0;
  padding: 0;
}
html, body, #app {
  height: 100%;
  overflow: hidden;
}
</style>

main.ts

import { createApp,createVNode,render } from 'vue'
import App from './App.vue'
import {router} from './router'
// import 引入
import ElementPlus from 'element-plus'
import 'element-plus/dist/index.css'
import loadingBar from './components/loadingBar.vue'

const Vnode = createVNode(loadingBar)
render(Vnode,document.body)
const app = createApp(App)
app.use(router)
// use 注入 ElementPlus 插件
app.use(ElementPlus)

const whiteList = ['/']

// beforeEach 可以定义不止一个，vue会收集所有定义的路由钩子，所以next的作用不应该是跳转，而是使步骤进行到下一个你定义的钩子
router.beforeEach((to, from, next) => {
  document.title = to.meta.title
  Vnode.component?.exposed?.startLoading()
  // token每次都要跟后端校验一下是否过期
  if(whiteList.includes(to.path) || localStorage.getItem('token')){
    next()
  }else{
    next('/')
  }
})

router.afterEach((to, from) => {
  Vnode.component?.exposed?.endLoading()
})
app.mount('#app')