当打包构建项目时， JavaScript 包会变得非常大，影响页面加载。如果我们能把不同路由对应的组件分割成不同的代码块，然后当路由被访问的时候才加载对应组件，这样就更加高效了。

具体需要 3 步：

① 安装 @babel/plugin-syntax-dynamic-import 包。

② 在 babel.config.js 配置文件中声明该插件。

③ 将路由改为按需加载的形式，示例代码如下：

const Foo = () => import(/* webpackChunkName: "group-foo" */ './Foo.vue')
const Bar = () => import(/* webpackChunkName: "group-foo" */ './Bar.vue')
const Baz = () => import(/* webpackChunkName: "group-boo" */ './Baz.vue')

关于路由懒加载的详细文档，可参考如下链接：

https://router.vuejs.org/zh/guide/advanced/lazy-loading.html

foo和bar的分组名称都叫做group-foo

这两个文件会同时被打包到同一个js文件中，请求foo的时候，会同时把bar请求过来。

在安装好依赖之后，把之前的路由全部改装成懒加载的形式

const+组件的名称，然后是组件的分组名称和存放路径，

希望把哪几个放在一个js文件中，就起相同的分组名称

分组名称通常命名为组件的名称合集

// import Login from '../components/login.vue'
const Login = () => import(/* webpackChunkName: "login_home_welcome" */ '../components/login.vue')
// import Home from '../components/home.vue'
const Home = () => import(/* webpackChunkName: "login_home_welcome" */ '../components/home.vue')
// import Welcome from '../components/welcome.vue'
const WelCome = () => import(/* webpackChunkName: "login_home_welcome" */ '../components/welcome.vue')

// import Users from '../components/user/Users.vue'
const  Users  = () => import(/* webpackChunkName: "Users_Rights_Roles" */ '../components/user/Users.vue')
// import Rights from '../components/power/Rights.vue'
const   Rights  = () => import(/* webpackChunkName: "Users_Rights_Roles" */ '../components/power/Rights.vue')
// import Roles from '../components/power/Roles.vue'
const Roles = () => import(/* webpackChunkName: "Users_Rights_Roles" */ '../components/power/Roles.vue')


// import Cate from '../components/goods/Cate.vue'
const  Cate = () => import(/* webpackChunkName: "Cate_Params" */ '../components/goods/Cate.vue')
// import Params from '../components/goods/Params.vue'
const Params = () => import(/* webpackChunkName: "Cate_Params" */ '../components/goods/Params.vue')

// import GoodsList from '../components/goods/List.vue'
const GoodsList = () => import(/* webpackChunkName: "GoodsList_Add" */ '../components/goods/List.vue')
// import Add from '../components/goods/add.vue'
const Add = () => import(/* webpackChunkName: "GoodsList_Add" */ '../components/goods/add.vue')

// import Order from '../components/order/Order.vue'
const Order = () => import(/* webpackChunkName: "Order_Report" */ '../components/order/Order.vue')
// import Report from '../components/report/Report.vue'
const Report = () => import(/* webpackChunkName: "Order_Report" */ '../components/report/Report.vue')