Detailed explanation of optimization steps using vue-admin-template

This time I will bring you a detailed explanation of the optimization steps for using vue-admin-template. What are the precautions for using vue-admin-template optimization? The following is a practical case, let's take a look.

Preface

The company has several projects with backend management systems. In order to facilitate development, we chose the popular backend template in vue. Developed as a basic template. However, when I started using it, the author did not optimize this. When the project went online, I discovered that the packaged files were very large, with just one vendor having a volume of 770k (the picture below is the basic template, everything is No packaged file information is added):

can be analyzed through webpack-bundle-analyzer. The volume mainly comes from the Ele.me UI ( The volume is 500k), because the split components were not partially introduced, causing webpack to package the entire component library. The second is vue itself, which has a size of 80k.

# Therefore, it is urgent to optimize its packaging.

Optimization

The main purposes of optimization are:

1. Speed ​​up resource loading and reduce user waiting time and home page white screen time to improve user experience.

2. Speed ​​up packaging and don’t waste time waiting for packaging.

To solve the first problem, many people will think that resource files can be placed on CDN. Yes, this time we will solve the loading problem through CDN.

CDN - Improve loading speed

More mature frameworks/component libraries like vue and element ui generally have free, high-speed, The public cdn is for developers to use. Since most users are in China, the bootcdn library is used this time. The popular resources of this library are relatively complete, available in various versions, and the domestic access speed is very fast, which is simply good news for developers.

Introduce vue and Ele.me components into index.html.

nbsp;html>

 
  <meta>
  <meta>
  <title>vue-admin-template</title>
  <!-- 同时也要引入对应版本的 css -->
  <link>
 
 
  <p></p>
  <!-- built files will be auto injected -->
  <!-- 先引入 Vue -->
  <script></script>
  <!-- 引入组件库 -->
  <script></script>
  <script></script>
 

Because dependencies are introduced from outside, webpack needs to be informed of the source of dependencies when packaging.

Modifywebpack.base.conf.js:

module.exports = {
 ...
 externals: {
  vue: 'Vue',
  'element-ui':'ELEMENT'
 }
}

Packaging it again can indeed greatly compress the packaging volume, from 700k to 130k:

But then there is a problem:

Obviously I am developing locally, but due to the introduction The online production version of the vue file is removed, so vue-dev-tools cannot be debugged.

Therefore, we need to adjust the webpack configuration again, webpack.base.conf.js, and the js injected by webpack is always at the end, so we need html-webpack-include-assets-plugin helps to inject app.js and then inject the corresponding component library:

const HtmlWebpackIncludeAssetsPlugin = require('html-webpack-include-assets-plugin')
const externals = {
 // 因为打包时，还没注入，所以这里要去掉。
 // 'element-ui':'ELEMENT'
}
// 生产环境中使用生产环境的 vue
// 开发环境继续使用本地 node_modules 中的 vue
if (process.env.NODE_ENV === 'production') {
 externals['vue'] = 'Vue'
 // 如发现打包时依旧将 element-ui 打包进入 vendor，可以在打包时将其加入外部依赖。
 externals['element-ui'] = 'ELEMENT'
}
// 生产环境默认注入 vue 
// 开发环境中不注入
const defaultJS = process.env.NODE_ENV === 'production' ? [{ path: 'https://cdn.bootcss.com/vue/2.4.2/vue.min.js', type: 'js' }] : []
const plugins = [
 new HtmlWebpackIncludeAssetsPlugin({
   assets: defaultJS.concat([
    { path: 'https://cdn.bootcss.com/element-ui/2.3.2/index.js', type: 'js' },
    { path: 'https://cdn.bootcss.com/element-ui/2.3.2/locale/zh-CN.min.js', type: 'js' },
   ]),
   // 是否在 webpack 注入的 js 文件后新增？true 为 append, false 为 prepend。
   // 生产环境中，这些 js 应该先加载。
   append: process.env.NODE_ENV !== 'production',
   publicPath: '',
  })
]
module.exports = {
 ...
 externals,
 plugins,
 ...
}

OK. At this time, both packaging and The final size can also be debugged using vue-dev-tool in development mode.

DLL - Improve packaging speed

# Front-ends that often package will find that many times, in order to fix certain bugs (such as promise in ie bug under Safari), and a new polyfill was introduced. However, after packaging, it was found that the hash value of the vendor has changed, and the entire vendor only added a new dependency of es6-promise, but it cost The price is that the previously packaged vendor needs to be discarded, and when the user revisits, they need to pull a brand new vendor again, which is a bit expensive.

At this time, using dllPlugin packaging has advantages. It can package some basic dependent modules together first. When officially packaging, these modules can be skipped and no longer packaged into the vendor repeatedly. This improves the packaging speed and also reduces the size of the vendor.

如，后台管理系统基础模块基本有以下几个：

1. axios： ajax 请求。

2. vuex： 全局状态管理。

3. js-cookie： 前端处理 cookie

4. vue-router： 路由管理。

这四个基础模块几乎是必须的，那么可以先提取出来。

step 1 打包基础模块

先在 build 文件夹下新建一个用于打包 dll 的配置文件 webpack.dll.conf.js：

const webpack = require('webpack');
const path = require('path');
const vueLoaderConfig = require('./vue-loader.conf')
const utils = require('./utils')
function resolve(dir) {
  return path.join(dirname, '..', dir)
}
const vendor = [
  // 'vue/dist/vue.runtime.esm.js', // 由于 vue 在生产环境中使用的是 cdn 引入，所以也无需提前打包进 dll
  // 'raven-js', // 前端监控，若无此需求，可以忽略。
  'es6-promise', // 修复 promise 中某些 bug。
  'vue-router',
  'js-cookie',
  'axios',
  'vuex',
];
const webpackConfig = {
  context: dirname,
  output: {
    path: path.join(dirname, '../static/js/'),
    filename: '[name].dll.js',
    library: '[name]_[hash]',
  },
  entry: {
    vendor
  },
  plugins: [
    new webpack.DllPlugin({
      context: dirname,
      path: path.join(dirname, '.', '[name]-manifest.json'),
      name: '[name]_[hash]',
    }),
    new webpack.optimize.UglifyJsPlugin({
      compress: {
       warnings: false
      },
      sourceMap: true,
      // parallel: true
    })
  ],
  module: {
    rules: [{
        test: /\.vue$/,
        loader: 'vue-loader',
        options: vueLoaderConfig
      },
      {
        test: /\.js$/,
        loader: 'babel-loader',
        include: [resolve('src'), resolve('test'), resolve('node_modules/webpack-dev-server/client')]
      },
      {
        test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('img/[name].[hash:7].[ext]')
        }
      },
      {
        test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('media/[name].[hash:7].[ext]')
        }
      },
      {
        test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
        }
      }
    ]
  }
};
module.exports = webpackConfig

然后在 package.json 中加入一条命令：

{
  "scripts": {
    ...
    "build:dll": "webpack --config build/webpack.dll.conf.js",
    ...
  }
}

执行 yarn build:dll 或者 npm run build:dll 即可完成打包 dll。执行完成后：

yarn build:dll
yarn run v1.5.1
$ webpack --config build/webpack.dll.conf.js
Hash: f6894dff019b2e0734af
Version: webpack 3.10.0
Time: 1295ms
     Asset   Size Chunks       Chunk Names
vendor.dll.js 62.6 kB    0 [emitted] vendor
  [8] dll vendor 12 bytes {0} [built]
  + 32 hidden modules
✨ Done in 1.89s.

同时，可以在 build 目录下，找到各个模块对应关系文件 vendors-manifest.json 和 static/js 下的 vendor.dll.js。

step 2 页面中引入 vendor

打包后的 dll 文件需要手动在 index.html 引入：

<p></p>
<!-- built files will be auto injected -->
<script></script>

step 3 告诉 webpack 使用 dllPlugin 进行打包

修改 build/webpack.prod.conf.js:

module.exports = {
  plugins: [
    ...
    new webpack.DllReferencePlugin({
      context: dirname,
      manifest: require('./vendor-manifest.json')
    }),
    ...
  ]
}

再次打包：

$ yarn build:report
yarn run v1.5.1
$ npm_config_report=true node build/build.js
Hash: b4ff51852866ed865cfd
Version: webpack 3.10.0
Time: 6532ms
                       Asset    Size Chunks       Chunk Names
     static/js/manifest.42b9584a653aec2b9c5e.js   1.5 kB    5 [emitted] manifest
             static/img/404.a57b6f3.png  98.1 kB     [emitted]
        static/js/1.9e4133a25808e2101dd3.js    1 kB    1 [emitted]
        static/js/2.2a8a8e01c51473fab882.js  4.34 kB    2 [emitted]
      static/js/vendor.c7b076ef3341d4711402.js  39.4 kB    3 [emitted] vendor
       static/js/app.6d52c7a5bf1bacb5cc85.js  21.4 kB    4 [emitted] app
        static/js/0.cbc645864aab28ae8055.js  15.3 kB    0 [emitted]
static/css/app.1b30f8eba210e245a5f96d7bf0d6fb6c.css   7.6 kB    4 [emitted] app
                    favicon.ico  67.6 kB     [emitted]
                     index.html 986 bytes     [emitted]
              static/js/vendor.dll.js  62.6 kB     [emitted]
 Build complete.
 Tip: built files are meant to be served over an HTTP server.
 Opening index.html over file:// won't work.

发现 vendor 现在只有 40k 的体积，减少了一半的体积，而且打包速度也快了 2s，而相对于最开始的基础模板，打包速度快了 12s，这是很让人欣慰。

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