一 点睛
当打包构建项目时,JavaScript包会变得非常大,影响页面的加载。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,在开发依赖中安装
2 在babel.config.js配置文件中声明该插件。
// 这是项目发布阶段需要用到的 babel 插件
const prodPlugins = []
if (process.env.NODE_ENV === 'production') {
prodPlugins.push('transform-remove-console')
}
module.exports = {
"presets": [
"@vue/cli-plugin-babel/preset"
],
"plugins": [
[
"component",
{
"libraryName": "element-ui",
"styleLibraryName": "theme-chalk"
}
],
// 发布产品时候的插件数组
...prodPlugins,
// 配置插件
'@babel/plugin-syntax-dynamic-import'
]
}
3 将路由改为按需加载的形式,示例代码如下:
import Vue from 'vue'
import VueRouter from 'vue-router'
// 导入登录组件
//import Login from "../components/Login";
// 导入Home 组件
//import Home from "../components/Home";
// 导入Welcome 组件
//import Welcome from "../components/Welcome";
// 改造成懒加载
const Login = () => import(/* webpackChunkName: "login_home_welcome" */ '../components/Login')
const Home = () => import(/* webpackChunkName: "login_home_welcome" */ '../components/Home')
const Welcome = () => import(/* webpackChunkName: "login_home_welcome" */ '../components/Welcome')
// 导入 Users 组件
// import Users from "../components/user/Users";
// 导入权限列表 组件
// import Rights from "../components/power/Rights";
// 导入角色列表 组件
// import Roles from "../components/power/Roles";
// 改造成懒加载
const Users = () => import(/* webpackChunkName: "users_rights_roles" */ '../components/user/Users')
const Rights = () => import(/* webpackChunkName: "users_rights_roles" */ '../components/power/Rights')
const Roles = () => import(/* webpackChunkName: "users_rights_roles" */ '../components/power/Roles')
// 导入商品分类 组件
import Cate from "../components/goods/Cate";
// 导入商品分类参数 组件
import Params from "../components/goods/Params";
// 改造成懒加载
//const Cate = () => import(/* webpackChunkName: "Cate_Params" */ '../components/goods/Cate')
//const Params = () => import(/* webpackChunkName: "Cate_Params" */ '../components/goods/Params')
// 导入商品列表组件
//import GoodsList from "../components/goods/List";
// 导入增加商品名称组件
//import Add from "../components/goods/Add";
// 改造成懒加载
const GoodsList = () => import(/* webpackChunkName: "GoodsList_Add" */ '../components/goods/List')
const Add = () => import(/* webpackChunkName: "GoodsList_Add" */ '../components/goods/Add')
// 导入订单组件
//import Order from "../components/order/Order";
// 导入报表功能
//import Report from "../components/report/Report";
// 改造成懒加载
const Order = () => import(/* webpackChunkName: "Order_Report" */ '../components/order/Order')
const Report = () => import(/* webpackChunkName: "Order_Report" */ '../components/report/Report')
import {renderThumbStyle} from "element-ui/packages/scrollbar/src/util";
Vue.use(VueRouter)
const routes = [
// 路由重定向,当访问/,就会重定向到/login
{
path: '/',
redirect: '/login'
},
// 定义登录路由规则
{
path: '/login',
component: Login
},
// 定义Home的路由规则
{
path: '/home',
component: Home,
redirect: '/welcome',
children: [
{
path: '/welcome',
component: Welcome
},
/* 用户管理 */
{
path: '/users',
component: Users
},
/* 权限管理 */
{
path: '/rights',
component: Rights
},
/* 角色管理 */
{
path: '/roles',
component: Roles
},
/* 商品分类 */
{
path: '/categories',
component: Cate
},
/* 商品分类参数 */
{
path: '/params',
component: Params
},
/* 商品列表 */
{
path: '/goods',
component: GoodsList
},
/* 增加商品 */
{
path: '/goods/add',
component: Add
},
/* 订单 */
{
path: '/orders',
component: Order
},
/* 报表 */
{
path: '/reports',
component: Report
}
]
}
]
const router = new VueRouter({
routes
})
// 挂载路由导航守卫
// to 将要访问的路径
// from 代表从哪个路径跳转而来
// next 是个函数,表示放行 next() 放行 next('/login') 强制跳转
router.beforeEach((to, from, next) => {
// 如果用户访问的登录页,直接放行
if (to.path === '/login') return next();
// 从 sessionStorage 中获取到保存的 token 值
const tokenstr = window.sessionStorage.getItem('token')
// 没有 token,强制跳转到登录页
if (!tokenstr) return next('/login')
next()
})
export default router