由于我的服务器是真的辣鸡，就迫使我优化项目提高项目加载速度。减少代码体积迫在眉睫，好在elementUI可以按需引入，而我项目又不需要这么多组件。elementUI按需引入真香，嘿嘿。

elementUI按需引入

1、安装elementUI

npm i element-ui -S

2、安装babel-plugin-component

借助 babel-plugin-component，我们可以只引入需要的组件，以达到减小项目体积的目的。
npm install babel-plugin-component -D

3、根目录babel.config.js添加如下代码

module.exports = {
  presets: [
    '@vue/cli-plugin-babel/preset',
  ],
  // 从这里开始--------------------------
  "plugins": [
    [
      "component",
      {
        "libraryName": "element-ui",
        "styleLibraryName": "theme-chalk"
      }
    ]
  ]
  // 这里结束----------------------------
}

4、在plugins文件夹里创建element.js，在element.js里写组件引入代码。完整引入如下：

import Vue from 'vue';
import {
  Pagination,
  Dialog,
  Autocomplete,
  Dropdown,
  DropdownMenu,
  DropdownItem,
  Menu,
  Submenu,
  MenuItem,
  MenuItemGroup,
  Input,
  InputNumber,
  Radio,
  RadioGroup,
  RadioButton,
  Checkbox,
  CheckboxButton,
  CheckboxGroup,
  Switch,
  Select,
  Option,
  OptionGroup,
  Button,
  ButtonGroup,
  Table,
  TableColumn,
  DatePicker,
  TimeSelect,
  TimePicker,
  Popover,
  Tooltip,
  Breadcrumb,
  BreadcrumbItem,
  Form,
  FormItem,
  Tabs,
  TabPane,
  Tag,
  Tree,
  Alert,
  Slider,
  Icon,
  Row,
  Col,
  Upload,
  Progress,
  Spinner,
  Badge,
  Card,
  Rate,
  Steps,
  Step,
  Carousel,
  CarouselItem,
  Collapse,
  CollapseItem,
  Cascader,
  ColorPicker,
  Transfer,
  Container,
  Header,
  Aside,
  Main,
  Footer,
  Timeline,
  TimelineItem,
  Link,
  Divider,
  Image,
  Calendar,
  Backtop,
  PageHeader,
  CascaderPanel,
  Loading,
  MessageBox,
  Message,
  Notification
} from 'element-ui';

Vue.use(Pagination);
Vue.use(Dialog);
Vue.use(Autocomplete);
Vue.use(Dropdown);
Vue.use(DropdownMenu);
Vue.use(DropdownItem);
Vue.use(Menu);
Vue.use(Submenu);
Vue.use(MenuItem);
Vue.use(MenuItemGroup);
Vue.use(Input);
Vue.use(InputNumber);
Vue.use(Radio);
Vue.use(RadioGroup);
Vue.use(RadioButton);
Vue.use(Checkbox);
Vue.use(CheckboxButton);
Vue.use(CheckboxGroup);
Vue.use(Switch);
Vue.use(Select);
Vue.use(Option);
Vue.use(OptionGroup);
Vue.use(Button);
Vue.use(ButtonGroup);
Vue.use(Table);
Vue.use(TableColumn);
Vue.use(DatePicker);
Vue.use(TimeSelect);
Vue.use(TimePicker);
Vue.use(Popover);
Vue.use(Tooltip);
Vue.use(Breadcrumb);
Vue.use(BreadcrumbItem);
Vue.use(Form);
Vue.use(FormItem);
Vue.use(Tabs);
Vue.use(TabPane);
Vue.use(Tag);
Vue.use(Tree);
Vue.use(Alert);
Vue.use(Slider);
Vue.use(Icon);
Vue.use(Row);
Vue.use(Col);
Vue.use(Upload);
Vue.use(Progress);
Vue.use(Spinner);
Vue.use(Badge);
Vue.use(Card);
Vue.use(Rate);
Vue.use(Steps);
Vue.use(Step);
Vue.use(Carousel);
Vue.use(CarouselItem);
Vue.use(Collapse);
Vue.use(CollapseItem);
Vue.use(Cascader);
Vue.use(ColorPicker);
Vue.use(Transfer);
Vue.use(Container);
Vue.use(Header);
Vue.use(Aside);
Vue.use(Main);
Vue.use(Footer);
Vue.use(Timeline);
Vue.use(TimelineItem);
Vue.use(Link);
Vue.use(Divider);
Vue.use(Image);
Vue.use(Calendar);
Vue.use(Backtop);
Vue.use(PageHeader);
Vue.use(CascaderPanel);

Vue.use(Loading.directive);

Vue.prototype.$loading = Loading.service;
Vue.prototype.$msgbox = MessageBox;
Vue.prototype.$alert = MessageBox.alert;
Vue.prototype.$confirm = MessageBox.confirm;
Vue.prototype.$prompt = MessageBox.prompt;
Vue.prototype.$notify = Notification;
Vue.prototype.$message = Message;

5、main.js里引入element.js

// 按需引入element组件
import './plugins/element.js'

注意！！！

按需引入不需要单独引入样式！！！
写了下面这句

import 'element-ui/lib/theme-chalk/index.css'

打包后代码大小：