vue cli3.0 首次加载优化

项目经理要求做首页加载优化，打包后从十几兆优化到两兆多，记下来怕下次忘记

运行report脚本 可看到都加载了那些内容，在从dist文件中index.html 查看首次加载都加载了那些东西，如下图：然后首次加载不需要用到的插件可不用在main.js中引入

 "dev": "vue-cli-service serve",
    "pro": "vue-cli-service serve --open --mode production",
    "build:prod": "vue-cli-service build",
    "report": "vue-cli-service build --report",

1、压缩  compression-webpack-plugin

const CompressionPlugin = require('compression-webpack-plugin');
const productionGzipExtensions = ["js", "css", "png", "jpeg", "jpg", "json", "geojson"];

plugins: [

      // new BundleAnalyzerPlugin(),

      new CompressionPlugin({

        algorithm: 'gzip', // 使用gzip压缩

        test: new RegExp('\\.(' + productionGzipExtensions.join('|') + ')$'), // 匹配文件名

        filename: '[path].gz[query]', // 压缩后的文件名(保持原文件名，后缀加.gz)

        minRatio: 0.8, // 压缩率小于0.81才会压缩

        threshold: 10240, // 对超过10k的数据压缩

        deleteOriginalAssets: false, // 是否删除未压缩的源文件，谨慎设置，如果希望提供非gzip的资源，可不设置或者设置为false（比如删除打包后的gz后还可以加载到原始资源文件

      })

    ]

 2、减少bn.js重复打包

 resolve: {

      alias: {

        '@': resolve('src'),

        'bn.js': path.resolve(process.cwd(), 'node_modules', 'bn.js')

      }

    },

　　

优化前：

优化后：

 3.element 在main中按需引入 打开report.html 会看到减少了common.js；

1、安装 babel-plugin-component

2、在babel.config.js配置
"plugins": [
    [
      "component",
      {
        "libraryName": "element-ui",
        "styleLibraryName": "theme-chalk"
      }
    ]
  ]

4、echarts  按需加载 注意echarts版本

1. 在main.js引入

import "@/utils/echarts-utils.js";
import * as echarts from 'echarts/core'
Vue.prototype.$echarts = echarts

echarts.reInit = function (chartDom) {
  if (chartDom != null) {
    echarts.dispose(chartDom);
  }
  return echarts.init(chartDom);
}

2.util.js

import * as echarts from 'echarts/core'

import { BarChart,LineChart,PieChart } from 'echarts/charts';

// 引入提示框，标题，直角坐标系，数据集，内置数据转换器组件，组件后缀都为 Component

import {

  TitleComponent,

  TooltipComponent,

  GridComponent,

  DatasetComponent,

  TransformComponent,

  ToolboxComponent,

  LegendComponent

} from 'echarts/components';

// 标签自动布局，全局过渡动画等特性

import { LabelLayout, UniversalTransition } from 'echarts/features';

// 引入 Canvas 渲染器，注意引入 CanvasRenderer 或者 SVGRenderer 是必须的一步

import { CanvasRenderer } from 'echarts/renderers';

// 注册必须的组件

echarts.use([

  TitleComponent,

  TooltipComponent,

  GridComponent,

  DatasetComponent,

  TransformComponent,

  ToolboxComponent,

  BarChart,

  LineChart,

  PieChart,

  LegendComponent,

  LabelLayout,

  UniversalTransition,

  CanvasRenderer

]);

5、分割  splitChunks

 chainWebpack(config) {
config
      .when(process.env.NODE_ENV !== 'development',
        config => {
          config
            .plugin('ScriptExtHtmlWebpackPlugin')
            .after('html')
            .use('script-ext-html-webpack-plugin', [{
              // `runtime` must same as runtimeChunk name. default is `runtime`
              inline: /runtime\..*\.js$/
            }])
            .end()
          config
            .optimization.splitChunks({
              chunks: 'all',
              cacheGroups: {
                libs: {
                  name: 'chunk-libs',
                  test: /[\\/]node_modules[\\/]/,
                  priority: 10,
                  chunks: 'initial' // only package third parties that are initially dependent
                },
                elementUI: {
                  name: 'chunk-elementUI', // split elementUI into a single package
                  priority: 20, // the weight needs to be larger than libs and app or it will be packaged into libs or app
                  test: /[\\/]node_modules[\\/]_?element-ui(.*)/ // in order to adapt to cnpm
                },
                commons: {
                  name: 'chunk-commons',
                  test: resolve('src/components'), // can customize your rules
                  minChunks: 3, //  minimum common number
                  priority: 5,
                  reuseExistingChunk: true
                }
              }
            })
          // https:// webpack.js.org/configuration/optimization/#optimizationruntimechunk
          config.optimization.runtimeChunk('single')
        }
      )
  }

6、小小的建议：静态文件图片等资源 尽量不需要放在同一个文件里面，不然的话首页没用到的图片的都会加载。