使用WebPack CommonsChunkPlugin提取重复的javascript代码

Question

我使用WebPack CommonsChunkPlugin提取重复代码并减少JavaScript代码大小。我有两个html页面和两个条目。此外，我还添加了ReactJs、供应商条目。到目前为止，在webpack.config.js中我们有：

var path = require("path");
var webpack = require('webpack');
var BundleTracker = require('webpack-bundle-tracker');
var BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;

module.exports = {
    context: __dirname,
    entry: {
        react: ["react", "react-dom"],
        home: './assets/js/home.jsx',
        about: './assets/js/about.jsx',
    },

    output: {
        path: path.resolve('./assets/bundles/'),
        filename: "[name].js",
    },

    plugins: [
        new BundleTracker({filename: './webpack-stats.json'}),

        new webpack.optimize.CommonsChunkPlugin({
            name: 'react',
            minChunks: Infinity
        }),

        new BundleAnalyzerPlugin(),
    ],

    module: {
        rules: [
            {
              test: /\.jsx?$/, 
              exclude: /node_modules/,
              loader: 'babel-loader',
              options: { 
                  plugins: [["lodash", { "id": ["semantic-ui-react"] }]],
                  presets: ["es2015", "react"]
              }  
            },
        ],
    },

    resolve: {
        modules: ['node_modules', 'bower_components'],
        extensions: ['*', '.js', '.jsx']
    },
};

此配置结果使用webpack-bundle-analyzer

​

​

正如你所看到的，有一些重复的代码，一些在红色区域，另一些在绿色区域。我想将这些js代码从家中提取出来，并将其打包到一个单独的包中。为了提取红色区域代码，即库，我在webpack配置中添加了以下行：

new webpack.optimize.CommonsChunkPlugin({
    name: 'lodash',
    minChunks: function(module, count) {
        return module.context.indexOf('node_modules/lodash') >= 0;
    }
}), 

但是它并没有像预期的那样工作，同时寄存库代码仍然在家里和关于捆绑包中，webpack还创建了一个名为协调性的包，它几乎是空的，并且不包含js库。

知道怎么修吗？提取绿色代码如何？

Answer 1

我通过在插件中添加一个公共块来解决这个问题。所以最后webpack的配置是：

var path = require("path");
var webpack = require('webpack');
var BundleTracker = require('webpack-bundle-tracker');

module.exports = {

    context: __dirname,

    entry: {
        react: ["react", "react-dom"],
        home: './assets/js/home.jsx',
        about: './assets/js/about.jsx',
    },

    output: {
        path: path.resolve('./assets/bundles/'),
        filename: "[name].js",
    },

    plugins: [

        new BundleTracker({filename: './webpack-stats.json'}),

        new webpack.optimize.CommonsChunkPlugin({
            name: 'react',
            filename: '[name].js',
            minChunks: Infinity,
        }),

        new webpack.optimize.CommonsChunkPlugin({
            name: 'common',
            chunks: ['home', 'about'],
            filename: '[name].js',
        }),
    ],

    module: {
        rules: [
            {
                test: /\.jsx?$/, 
                exclude: /node_modules/,
                loader: 'babel-loader',
                options: { 
                    plugins: [
                      ["lodash", { "id": ["semantic-ui-react"] }]
                    ],
                    presets: ["es2015", "react"]
                }
            },
        ],
    },

    resolve: {
        modules: ['node_modules', 'bower_components'],
        extensions: ['*', '.js', '.jsx']
    },
};

现在，bundle分析器的输出如下：

​

​

如图中所示，公共语义-ui反应库和存档库现在只是一个公共的包，不再重复了。

Answer 2

您的问题是，您在每个.js/.jsx文件中导入第三方库，而不是以前在公共文件(通常称为vendor.js)中导入它。

如果您有一个导入所有依赖项的文件，并且将它作为条目并包含到CommonsChunkPlugin中，webpack将不再将您的库包含在最后的包中(home.js和about.js)。这种技术被称为webpack文档中的代码分裂。

vendor.js (或适合您的名称)

import 'react';
import 'react-dom';
import 'lodash';
import 'semantic-ui-react';
//... all your npm packages

webpack.config.js

var webpack = require('webpack');
var path = require('path');

module.exports = {
    context: __dirname,
    entry: {
        vendor: './assets/js/vendor.js,
        home: './assets/js/home.jsx',
        about: './assets/js/about.jsx',
    },
    output: {
        path: path.resolve('./assets/bundles/'),
        filename: '[name].js',
    },
    plugins: [
        new webpack.optimize.CommonsChunkPlugin({
            name: 'vendor',
            minChunks: Infinity
        }),
    ],

    //Rest of Your config ...
};

index.html

<body>
    <!-- AFTER YOUR HTML CODE -->

    <script type="text/javascript" src="/assets/bundles/vendor.js"></script>
    <script type="text/javascript" src="/assets/bundles/home.js"></script>
    <script type="text/javascript" src="/assets/bundles/about.js"></script>
</body>

​

查看webpack代码拆分文档：

• 旧文档：https://webpack.github.io/docs/code-splitting.html#split-app-and-vendor-code
• 新文档：https://webpack.js.org/plugins/commons-chunk-plugin/#explicit-vendor-chunk