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接上回 《高性能流媒体服务器EasyDSS前端重构(一)-从零开始搭建 webpack + vue + AdminLTE 多页面脚手架》

在上一篇博客中, 我们白手起家, 从零搭建了 webpack + vue + AdminLTE 多页面脚手架. 代码在这里: easydss-web-src , 我为第一篇博客建立了单独的分支 blog_1 , 并且我打算后面的系列都这样, 建立一个单独分支.

为什么要提取共用文件

我们已经创建了两个静态页面: index.html 和 about.html, 对应的入口 js 分别是 index.js 和 about.js.

运行编译

npm run build

build 两个如此简单的两个页面, 耗时 6 秒多, 可以预见在实际开发中将面临 build 耗时长的问题. 并且我们看到 build 后的 js 文件达到 1.05MB 之大. 实际上, index.js 和 about.js 两者是有共用部分的, 这其中包括 jquery , vue, AdminLTE 这些基础组件. 本篇的主题就是介绍如何提取这部分共用的组件出来单独编译.

webpack.DllPlugin

类似于 Windows 中 DLL 动态库的概念, 在 webpack 2 当中, 引入了 DllPlugin. 借助这个插件, 我们能够把共用的组件 build 到一块, 生成 vendor.js, 然后在静态页面中, 引用这个 vendor.js.

新建组件打包配置文件: webpack.dll.config.js

const HtmlWebpackPlugin = require('html-webpack-plugin');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const webpack = require('webpack');
const path = require('path');function resolve(dir) {return path.resolve(__dirname, dir)
}module.exports = {entry: {//提取共用组件, 打包成 vendor.jsvendor: ['jquery', 'vue', 'vuex', 'babel-polyfill','font-awesome/css/font-awesome.css', 'admin-lte/bootstrap/css/bootstrap.css','admin-lte/dist/css/AdminLTE.css', 'admin-lte/dist/css/skins/_all-skins.css','admin-lte/bootstrap/js/bootstrap.js', 'admin-lte/dist/js/app.js']},output: {path: resolve('dll'),filename: 'js/[name].[chunkhash:8].js',library: '[name]_library'},resolve: {extensions: ['.js', '.vue', '.json'],alias: {'vue$': 'vue/dist/vue.common.js','jquery$': 'admin-lte/plugins/jQuery/jquery-2.2.3.min.js'}},module: {rules: [{test: /\.css$/,loader: 'style-loader!css-loader'},{test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,loader: 'url-loader?limit=10000&name=images/[name].[hash:8].[ext]'},{test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,loader: 'url-loader?limit=10000&name=fonts/[name].[hash:8].[ext]'},{test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,loader: 'url-loader?limit=10000&name=media/[name].[hash:8].[ext]'}]},plugins: [new webpack.ProvidePlugin({$: 'jquery',jQuery: 'jquery',"window.jQuery": 'jquery',"window.$": 'jquery'}),         new webpack.HashedModuleIdsPlugin(),new CleanWebpackPlugin(['dll']),new webpack.DllPlugin({path: resolve("dll/[name]-manifest.json"),name: "[name]_library",context: __dirname}),new HtmlWebpackPlugin({filename: 'template.html',title: '<%= htmlWebpackPlugin.options.title %>',inject: 'head',chunks: ['vendor'],template: './src/template.html',minify: {removeComments: true,collapseWhitespace: false}})        ]
};

entry 当中, 指定哪些资源被视为共用组件
上面的配置将在当前目录下, 创建一个 dll 目录, 专门用来存放共用组件包 vendor.js, 并且生成一个 template.html, 这个 template.html 中包含对 vendor.js 的引用. template.html 将作为其他页面的基础模板使用, 这样一般静态页面就能够引用到 vendor.js 了.

webpack.DllReferencePlugin

DllReferencePlugin 这个插件用来告诉 webpack , 哪些引用到的资源已经被打包在共用组件包当中, 从而避免再次被打包.

我们来修改 webpack.config.js

const HtmlWebpackPlugin = require('html-webpack-plugin');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const webpack = require('webpack');
const path = require('path');
require("babel-polyfill");function resolve(dir) {return path.resolve(__dirname, dir)
}module.exports = {//定义页面的入口, 因为js中将要使用es6语法, 所以这里需要依赖 babel 垫片entry: {index: ['babel-polyfill', './src/index.js'],about: ['babel-polyfill', './src/about.js']},output: {path: resolve('dist'), // 指示发布目录filename: 'js/[name].[chunkhash:8].js' //指示生成的页面入口js文件的目录和文件名, 中间包含8位的hash值},//下面给一些常用组件和目录取别名, 方便在js中 importresolve: {extensions: ['.js', '.vue', '.json'],alias: {'vue$': 'vue/dist/vue.common.js','jquery$': 'admin-lte/plugins/jQuery/jquery-2.2.3.min.js','src': resolve('src'),'assets': resolve('src/assets'),'components': resolve('src/components')}},module: {//配置 webpack 加载资源的规则rules: [{test: /\.js$/,loader: 'babel-loader',include: [resolve('src')]}, {test: /\.vue$/,loader: 'vue-loader'}, {test: /\.css$/,loader: 'style-loader!css-loader'},{test: /\.less$/,loader: "less-loader"},{test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,loader: 'url-loader?limit=10000&name=images/[name].[hash:8].[ext]'},{test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,loader: 'url-loader?limit=10000&name=fonts/[name].[hash:8].[ext]'},{test: /\.(swf|mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,loader: 'url-loader?limit=10000&name=media/[name].[hash:8].[ext]'}]},plugins: [//引入全局变量new webpack.ProvidePlugin({$: 'jquery',jQuery: 'jquery',"window.jQuery": 'jquery',"window.$": 'jquery'}),new webpack.DllReferencePlugin({context: __dirname,manifest: require('./dll/vendor-manifest.json')}),new CopyWebpackPlugin([{ from: 'dll', ignore: ['template.html', 'vendor-manifest.json'] }]),//编译前先清除 dist 发布目录new CleanWebpackPlugin(['dist']),//生成视频广场首页, 在这个页面中自动引用入口 index --> dist/js/index.[chunkhash:8].js//以 src/index.html 这个文件作为模板new HtmlWebpackPlugin({filename: 'index.html',title: '视频广场',inject: true, // head -> Cannot find element: #appchunks: ['index'],template: './dll/template.html',minify: {removeComments: true,collapseWhitespace: false}}),//生成版本信息页面, 在这个页面中自动引用入口 about --> dist/js/about.[chunkhash:8].js//以 src/index.html 这个文件作为模板new HtmlWebpackPlugin({filename: 'about.html',title: '版本信息',inject: true,chunks: ['about'],template: './dll/template.html',minify: {removeComments: true,collapseWhitespace: false}})]
};

DllReferencePlugin 通过读取 ./dll/vendor-manifest.json, 判断哪些资源引用被打包在共用组件包
index.html 和 about.html 以 ./dll/template.html 作为模板, 从而获取对 vendor.js 的引用
引入 CopyWebpackPlugin 这个插件, 负责将共用组件包依赖的资源文件拷贝到发布目录下, 同时过滤掉发布时不需要的文件: template.html 和 vendor-manifest.json

使用新的编译方式

因为新引入 CopyWebpackPlugin 插件, 首先, 我们安装它

npm i copy-webpack-plugin --save-dev

修改 package.json , 添加 dll 编译配置:

{"name": "easydss-web-src","version": "1.0.0","description": "","main": "index.js","scripts": {"build": "webpack --progress --hide-modules","dll": "webpack --progress --hide-modules --config ./webpack.dll.config.js","start": "webpack-dev-server --open","test": "echo \"Error: no test specified\" && exit 1"},"keywords": [],"author": "","license": "ISC","devDependencies": {"admin-lte": "^2.3.11","babel-core": "^6.26.0","babel-loader": "^7.1.1","babel-polyfill": "^6.26.0","babel-preset-es2015": "^6.24.1","babel-preset-stage-2": "^6.24.1","clean-webpack-plugin": "^0.1.16","css-loader": "^0.28.5","file-loader": "^0.11.2","font-awesome": "^4.7.0","html-webpack-plugin": "^2.30.1","less": "^2.7.2","less-loader": "^4.0.5","style-loader": "^0.18.2","url-loader": "^0.5.9","vue": "^2.4.2","vue-loader": "^13.0.4","vue-template-compiler": "^2.4.2","vuex": "^2.3.1","webpack": "^3.5.5","webpack-dev-server": "^2.7.1"}
}

编译共用组件, 你可能在整个开发过程中, 只需要执行一次对共用组件的 build, 因为一般情况下, 我们很少会对它做改动, 这一点是我优化编译时间的关键.

npm run dll

编译静态页面, 这一次的耗时相对之前减少了 4 秒多.

npm run build

是不是离幸福又近了一点, 源码位置: easydss-web-src/tree/blog_2

下一篇介绍在此基础之上, 引入饿了么前端组件框架 element-ui

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