使用 WebPack CommonsChunkPlugin 提取重复的 javascript 代码

Question

我正在使用 WebPack CommonsChunkPlugin 来提取重复代码并减少 JavaScript 代码大小。我有两个 html 页和两个条目。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']
    },
};

此配置结果与 webpack-bundle-analyzer:

大家可以看到，有一些重复的代码，有的在红色区域，有的在绿色区域。我想从 home 和 about bundle 中提取这个 js 代码到一个单独的 bundle 中。要提取红色区域代码，即 lodash 库，我将这些行添加到 webpack 配置中：

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

但它没有按预期工作，lodash 库代码仍在 home 和 about 包中，webpack 还创建了一个名为 lodash 的包，它几乎是空的，不包含任何 js 库。

知道如何解决吗？提取绿色代码如何？

Answer 1

您的问题是您在每个 .js/.jsx 文件中导入第三方库，而不是之前在公共文件（通常称为 vendor.js）中导入它。
如果你有这个导入所有依赖项的文件，并将它作为入口包含到 CommonsChunkPlugin，webpack 将不会再次将你的库包含在你的最终包中（home.js 和 about.js).该技术在 webpack 文档中称为 code splitting。

vendor.js（或适合您情况的名称）

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：

Answer 2

我设法通过向插件添加一个公共块来解决问题。所以最终的 webpack 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']
    },
};

现在包分析器的输出是这样的：

如图所示，通用语义-ui-react 和 lodash 库现在只是在通用包中，不再重复。

使用 WebPack CommonsChunkPlugin 提取重复的 javascript 代码

Extract duplicate javascript code using WebPack CommonsChunkPlugin

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