webpack最小化lodash

- 日理万妓 2022-03-27 06:50 257阅读 0赞

`lodash`作为一个比较常用的前端开发工具集，在使用webpack进行`vendor`分离的实践中，会遇到将整个`lodash`文件分离到`vendor.js`的问题。这样会使`vendor.js`文件变得特别大。

`webpack.config.js`文件代码如下：

var path = require('path');
    
    module.exports = mode => {
        return {
            entry: {
                A: './moduleA.js',
                B: './moduleB.js',
                C: './moduleC.js',
            },
            mode: mode,
            output: {
                path: path.resolve(__dirname, 'dist/'),
                filename: '[name].js'
            },
            optimization: {
                usedExports: true,
                splitChunks: {
                    cacheGroups: {
                        commons: {
                            chunks: 'all',
                            minChunks: 2,
                            maxInitialRequests: 5,
                            minSize: 0
                        },
                        vendor: {
                            test: /node_modules/,
                            chunks: "initial",
                            name: "vendor",
                            priority: 10,
                            enforce: true
                        }
                    }
                }
            },
            module: { },
            plugins: [ ]
        }
    }

运行`npm run test`脚本命令，结果如下：

Hash: 5d86af7ed04c57cca071
    Version: webpack 4.28.4
    Time: 5707ms
    Built at: 2019-01-11 19:25:04
               Asset       Size  Chunks             Chunk Names
                A.js   1.46 KiB       3  [emitted]  A
                B.js   1.53 KiB       4  [emitted]  B
                C.js   1.54 KiB       5  [emitted]  C
    commons~A~B~C.js  132 bytes       0  [emitted]  commons~A~B~C
      commons~A~C.js  238 bytes       1  [emitted]  commons~A~C
           vendor.js   69.7 KiB       2  [emitted]  vendor
    Entrypoint A = vendor.js commons~A~B~C.js commons~A~C.js A.js
    Entrypoint B = commons~A~B~C.js B.js
    Entrypoint C = vendor.js commons~A~B~C.js commons~A~C.js C.js

如上面的情况，`vendor.js`文件为`69.7kb`，如果再引用了其他第三方库，文件会更大。

那么，如何在开发的过程中，压缩`lodash`呢？

## babel-loader & babel-plugin-lodash ##

可以使用`babel-loader`在对`*.js`文件进行解析，然后借助于`babel-plugin-lodash`插件对引用的`lodash`进行类似`tree shaking`的操作，这样就可以去除未使用的`lodash`代码片段。

安装所需依赖：

yarn add babel-loader  @babel/core @babel/preset-env babel-plugin-lodash --dev

像下面这样修改`webpack.config.js`配置文件：

...
    module: {
      rules: [
          {
              test: /\.js$/,
              exclude: /node_modules/,
              use: {
                  loader: 'babel-loader',
                  options: {
                      presets: ['@babel/preset-env'],
                      plugins: ['lodash']
                  }
              }
          }
      ]
    }
    ...

运行`npm run test`，脚本命令结果如下：

Hash: 30def5521978552cc93d
    Version: webpack 4.28.4
    Time: 3249ms
    Built at: 2019-01-11 21:25:23
               Asset       Size  Chunks             Chunk Names
                A.js   1.46 KiB       3  [emitted]  A
                B.js   1.53 KiB       4  [emitted]  B
                C.js   1.54 KiB       5  [emitted]  C
    commons~A~B~C.js  132 bytes       0  [emitted]  commons~A~B~C
      commons~A~C.js  226 bytes       1  [emitted]  commons~A~C
           vendor.js  502 bytes       2  [emitted]  vendor
    Entrypoint A = vendor.js commons~A~B~C.js commons~A~C.js A.js
    Entrypoint B = commons~A~B~C.js B.js
    Entrypoint C = vendor.js commons~A~B~C.js commons~A~C.js C.js

`vendor.js`文件从`69.7kb`降至`502bytes`。

根据[`babel-plugin-lodash`][babel-plugin-lodash]参考文档介绍，使用[`lodash-webpack-plugin`][lodash-webpack-plugin]可以进一步压缩`lodash`。

### lodash-webpack-plugin ###

安装`lodash-webpack-plugin`依赖：

yarn add lodash-webpack-plugin --dev

修改`webpack.config.js`配置文件如下：

var LodashModuleReplacementPlugin = require('lodash-webpack-plugin');
    
    ...
    plugins: [
        new LodashModuleReplacementPlugin,
    ]
    ...

运行`npm run test`脚本命令，结果如下所示：

Hash: 30def5521978552cc93d
    Version: webpack 4.28.4
    Time: 2481ms
    Built at: 2019-01-11 21:07:23
               Asset       Size  Chunks             Chunk Names
                A.js   1.46 KiB       3  [emitted]  A
                B.js   1.53 KiB       4  [emitted]  B
                C.js   1.54 KiB       5  [emitted]  C
    commons~A~B~C.js  132 bytes       0  [emitted]  commons~A~B~C
      commons~A~C.js  226 bytes       1  [emitted]  commons~A~C
           vendor.js  502 bytes       2  [emitted]  vendor
    Entrypoint A = vendor.js commons~A~B~C.js commons~A~C.js A.js
    Entrypoint B = commons~A~B~C.js B.js
    Entrypoint C = vendor.js commons~A~B~C.js commons~A~C.js C.js

`vendor.js`依然是`502 bytes`，问题不在`loadsh-webpack-plugin`，它虽然会进一步优化`lodash`，但是在无法进一步优化的情况下，它也没办法。

一般情况下，不使用`lodash-webpack-plugin`就可以满足开发的需要，但是文件特别大的情况下，建议还是使用它。

[参考源代码][Link 1]

来源：[https://segmentfault.com/a/1190000017862101][https_segmentfault.com_a_1190000017862101]

[babel-plugin-lodash]: https://www.npmjs.com/package/babel-plugin-lodash
[lodash-webpack-plugin]: https://www.npmjs.com/package/lodash-webpack-plugin
[Link 1]: https://github.com/lvzhenbang/webpack-learning/tree/master/demo/example-13
[https_segmentfault.com_a_1190000017862101]: https://segmentfault.com/a/1190000017862101