按需加载

1.对项目进行打包

 npm run build

2.安装babel-plugin-component插件

npm install babel-plugin-component -D

3.将 babel.config.js文件修改为以下内容

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

4.按需在src/main.js文件下引入Button和Message

import Vue from 'vue';
import App from './App.vue';
import 'element-ui/lib/theme-chalk/index.css';
import { Button, Message } from 'element-ui';

Vue.component(Button.name, Button);
/* 或写为
 * Vue.use(Button);
 */
Vue.prototype.$message = Message;

Vue.config.productionTip = false;

new Vue({
  render: h => h(App),
}).$mount('#app')

以下为完整组件列表和引入方式（完整组件列表以 components.json 为准）

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.重新对项目进行打包

 npm run build

按需加载后文件缩小了

全局配置

在引入 Element 时，可以传入一个全局配置对象。该对象目前支持size与zIndex字段。size 用于改变组件的默认尺寸，zIndex设置弹框的初始z-index（默认值：2000）。按照引入 Element 的方式，具体操作如下：

完整引入 Element：

import Vue from 'vue';
import App from './App.vue';
import Element from 'element-ui';
import 'element-ui/lib/theme-chalk/index.css';

Vue.use(Element, { size: 'small', zIndex: 3000 });
Vue.config.productionTip = false;

new Vue({
  render: h => h(App),
}).$mount('#app')

按需引入 Element：

import Vue from 'vue';
import App from './App.vue';
import 'element-ui/lib/theme-chalk/index.css';
import { Button, Message } from 'element-ui';

Vue.prototype.$ELEMENT = { size: 'small', zIndex: 3000 };
Vue.use(Button);
Vue.prototype.$message = Message;
Vue.config.productionTip = false;

new Vue({
  render: h => h(App),
}).$mount('#app')