配置 - 下载网

1.按需引入各类组件库

.babel.config.js

module.exports = {
  presets: [["@vue/app", { useBuiltIns: "entry" }]],
  plugins: [
    // element官方教程
    [
      "component",
      {
        libraryName: "element-ui",
        styleLibraryName: "theme-chalk"
      }
    ]
  ]
}

1.v-if 和 v-show选择调用少使用v-if 绑定key

2.细分vuejs组件组件细分，比如一个组件，可以把整个组件细分成轮播组件、列表组件、分页组件等。 3.减少watch的数据数据大时，系统会出现卡顿，所以减少watch的数据。

4.路由懒加载分割路由，当路由被访问的时候才加载对应的组件

  const router = new VueRouter({
   routes: [
     { path: '/foo', component:  () => import('./Foo.vue')}
   ]
 })

5.内容类系统的图片资源按需加载图片加载比较多，使用v-lazy之类的懒加载

  ```
   npm install vue-lazyload --save-dev
   import VueLazyload from 'vue-lazyload'
   Vue.use(VueLazyload)
   <img v-lazy="/static/img/1.png">
  ```
  手动清除各类事件监听器，定时器及闭包等

6.SSR(服务端渲染) 如果项目比较大，首屏无论怎么做优化，都出现闪屏或者一阵黑屏的情况。可以考虑使用SSR(服务端渲染)

7.vue functional 优化

8.Object.freeze 优化

9.减少http请求

10.减少缓存及dom操作

2. webpack 打包的优化

查看引入的各类包占比

在package.json 的scripts里加入 "report": "vue-cli-service build --report"
运行npm run report
在 dist 文件里找到report.html， 在浏览器打开即可

1.开启gzip压缩

// 下载
npm install compression-webpack-plugin --save-dev

const isProduction = ["production", "prod"].includes(process.env.NODE_ENV);
const CompressionWebpackPlugin = require('compression-webpack-plugin');
const productionGzipExtensions = /\.(js|css|json|txt|html|ico|svg)(\?.*)?$/i;

configureWebpack: config => {
    const plugins = [];
    if (isProduction) {
       plugins.push(
              new CompressionWebpackPlugin({
              filename: "[path].gz[query]",
              algorithm: "gzip",
              test: productionGzipExtensions,
              threshold: 10240,
              minRatio: 0.8
           })
       );
    }
  config.plugins = [...config.plugins, ...plugins];
}

2.splitChunks 单独打包第三方模块

  // webpack配置
  chainWebpack: (config) => {
    if (isProduction) {
      config.optimization.delete("splitChunks");
    }
    return config;
  },

  configureWebpack: config => {
  if (isProduction) {
    // 利用 splitChunks 单独打包第三方模块
    config.optimization = {
      splitChunks: {
        cacheGroups: {
          common: {
            name: "chunk-common",
            chunks: "initial",
            minChunks: 2,
            maxInitialRequests: 5,
            minSize: 0,
            priority: 1,
            reuseExistingChunk: true,
            enforce: true
          },
          vendors: {
            name: "chunk-vendors",
            test: /[\\/]node_modules[\\/]/,
            chunks: "initial",
            priority: 2,
            reuseExistingChunk: true,
            enforce: true
          },
          elementUI: {
            name: "chunk-elementui",
            test: /[\\/]node_modules[\\/]element-ui[\\/]/,
            chunks: "all",
            priority: 3,
            reuseExistingChunk: true,
            enforce: true
          },
          echarts: {
            name: "chunk-echarts",
            test: /[\\/]node_modules[\\/](vue-)?echarts[\\/]/,
            chunks: "all",
            priority: 4,
            reuseExistingChunk: true,
            enforce: true
          }
        }
      }
    };
  }
  config.plugins = [...config.plugins, ...plugins];
}

3.去除consollog

  configureWebpack: config => {
  const plugins = [];
  if (isProduction) {
    // 去除consollog
    plugins.push(
      new UglifyJsPlugin({
        uglifyOptions: {
          compress: {
            warnings: false,   // 打包报错可注掉
            drop_console: true,
            drop_debugger: false,
            pure_funcs: ["console.log"] //移除console
          },
        },
        sourceMap: false,
        parallel: true,
      })
    );
  }
  config.plugins = [...config.plugins, ...plugins];
}

4.压缩图片

   config.module
    .rule('images')
    .use('image-webpack-loader')
    .loader('image-webpack-loader')
    .options({
      bypassOnDebug: true
    })
  .end()

设置完后，打包后可以看到 .gz 结尾的文件，在http请求的Request Headers 中能看到AcceptEncoding:gzip。要使服务器返回.gz文件，还需要对服务器进行配置，根据Request Headers的Accept-Encoding标签进行鉴别，如果支持gzip就返回.gz文件。

完整vue.config.js


const path = require("path");
const UglifyJsPlugin = require("uglifyjs-webpack-plugin");
const CompressionWebpackPlugin = require("compression-webpack-plugin");
const productionGzipExtensions = /\.(js|css|json|txt|html|ico|svg)(\?.*)?$/i;
const isProduction = ["production", "prod", 'test'].includes(process.env.NODE_ENV);
const resolve = dir => path.join(__dirname, dir);

module.exports = {
  publicPath: "/", // 公共路径
  runtimeCompiler: true, // 是否使用包含运行时编译器的 Vue 构建版本
  outputDir: process.env.outputDir, // 不同的环境打不同包名
  pluginOptions: {
    "style-resources-loader": {
      preProcessor: "less",
      patterns: [
        // 这个是加上自己的路径，
        // 注意：试过不能使用别名路径
        path.resolve(__dirname, "./src/assets/css/variable.less")
      ]
    }
  },
  lintOnSave: false, // 关闭eslint
  productionSourceMap: false, // 生产环境下css 分离文件
  // css相关配置
  devServer: {
    // 配置服务器
    port: 8112,
    open: true,
    https: false,
    // disableHostCheck: true,
    // overlay: {
    //   warnings: false,
    //   errors: true
    // },
    proxy: {
      "/api/*": {
        target: process.env.VUE_APP_URL, // 目标 API 地址
        ws: true, // 是否代理 websockets
        changOrigin: true, // 跨域配置
        pathRewrite: {
          "^/api": "/"
        }
      },
      // "/common/*": {
      //   target: process.env.VUE_APP_MIPA_URL, // 目标 API 地址
      //   ws: true, // 是否代理 websockets
      //   changOrigin: true, // 跨域配置
      //   pathRewrite: {
      //     "^/common": "/"
      //   }
      // }
    }
  },
  // 兼容ie10
  // webpack配置
  chainWebpack: config => {
    // 移除 prefetch 插件
    config.plugins.delete('prefetch')
    // 移除 preload 插件
    config.plugins.delete('preload');
    // ie 兼容,与main.js引入，存在一个就可
    // config.entry("main").add("babel-polyfill");
    // 别名
    config.resolve.alias
      .set("@", resolve("src"))
      .set("@i", resolve("src/assets/image"));
    if (isProduction) {
      config.optimization.delete("splitChunks");
    }
    // 压缩图片
    // config.module
    //   .rule('images')
    //   .use('image-webpack-loader')
    //   .loader('image-webpack-loader')
    //   .options({
    //     bypassOnDebug: true
    //   })
    // .end()
    return config;
  },
  // 配置webpack
  configureWebpack: config => {
    const plugins = [];
    if (isProduction) {
      // 开启gzip压缩
      plugins.push(
        new CompressionWebpackPlugin({
          filename: "[path].gz[query]",
          algorithm: "gzip",
          test: productionGzipExtensions,
          threshold: 10240,
          minRatio: 0.8,
          deleteOriginalAssets: false // 删除原文件
        })
      );
      // 利用 splitChunks 单独打包第三方模块
      config.optimization = {
        splitChunks: {
          cacheGroups: {
            common: {
              name: "chunk-common",
              chunks: "all",
              minChunks: 2,
              maxInitialRequests: 5,
              minSize: 0,
              priority: 1,
              reuseExistingChunk: true,
              enforce: true
            },
            vendors: {
              name: "chunk-vendors",
              test: /[\\/]node_modules[\\/]/,
              chunks: "all",
              priority: 2,
              reuseExistingChunk: true,
              enforce: true
            },
            styles: {
              name: 'chunk-styles',
              test: /\.(sa|sc|le|c)ss$/,
              chunks: 'all',
              enforce: true,
            },
            elementUI: {
              name: "chunk-element-ui",
              test: /[\\/]node_modules[\\/]element-ui[\\/]/,
              chunks: "all",
              priority: 3,
              reuseExistingChunk: true,
              enforce: true
            },
            echarts: {
              name: "chunk-echarts",
              test: /[\\/]node_modules[\\/]echarts[\\/]/,
              chunks: "all",
              priority: 4,
              reuseExistingChunk: true,
              enforce: true
            },
            vue: {
              name: "chunk-vue",
              test: /[\\/]node_modules[\\/]vue[\\/]/,
              chunks: "all",
              priority: 5,
              reuseExistingChunk: true,
              enforce: true
            },
            xlsx: {
              name: "chunk-xlsx",
              test: /[\\/]node_modules[\\/]xlsx[\\/]/,
              chunks: 'all',
              priority: 6,
              reuseExistingChunk: true,
              enforce: true
            },
            runtimeChunk: {
              name: 'manifest'
            }
          }
        }
      };
      // 去除consollog
      plugins.push(
        new UglifyJsPlugin({
          uglifyOptions: {
            // 删除注释
            output: {
              comments: false
            },
            compress: {
              // warnings: false,
              drop_console: true,
              drop_debugger: false,
              pure_funcs: ["console.log"] //移除console
            }
          },
          sourceMap: false,
          parallel: true
        })
      );
    }
    config.plugins = [...config.plugins, ...plugins];
  }
};