React从入门到放弃之前奏(1)：webpack4简介

接触webpack是好久之前的事情了，最近看了下webpack没想到都到4了。

webpack 是一个现代 JavaScript 应用程序的静态模块打包器(module bundler).

会创建1个依赖关系图(dependency graph),包含所有依赖的模块，然后将模块打包成1个或多个bundle.

webpack4 仍然支持高度可配，但完全可以不用配置文件了(基于mode)。

安装

淘宝源：npm config set registry https://registry.npm.taobao.org

升级npm：npm i npm -g

安装webpack：npm i -D webpack webpack-cli webpack-dev-server

运行webpack：npx webpack(Node 8.2+ 版本提供的npx命令)

基本特性

核心配置：

• 入口(entry)：
• 输出(output)：
• loader：
• 插件(plugins)：

Entry

入口起点(entry point)指示 webpack 应该使用哪个模块，来作为构建其内部依赖图的开始。

可以通过在 webpack 配置中配置 entry 属性，来指定一个入口起点（或多个入口起点）。默认值为 ./src/index.js

webpack.config.js

module.exports = {
    entry: {
        main: './src/index.js'
    },
};

Output

output 属性告诉 webpack 在哪里输出它所创建的 bundles，以及如何命名这些文件，默认值为./dist/[name].js

webpack.config.js

const path = require('path');
module.exports = {
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js'
  }
};

Loader

loader 让 webpack 能够去处理那些非 JavaScript 文件（webpack 自身只理解 JavaScript）。

loaders 有2个核心参数：

1. test 属性，用于标识出需要转换的某个或某些文件。
2. use 属性，表示进行转换时，应该使用哪个 loader。

const path = require('path');
const config = {
  output: {
    filename: 'bundle.js'
  },
  module: {
    rules: [
      { test: /\.txt$/, use: 'raw-loader' }
    ]
  }
};
module.exports = config;

Plugins

插件的范围包括，从打包优化和压缩，一直到重新定义环境中的变量。插件接口功能极其强大，可以用来处理各种各样的任务。

webpack.config.js

const HtmlWebpackPlugin = require('html-webpack-plugin'); // 通过 npm 安装
const webpack = require('webpack'); // 用于访问内置插件
const config = {
  module: {
    rules: [
      { test: /\.txt$/, use: 'raw-loader' }
    ]
  },
  plugins: [
    new webpack.optimize.UglifyJsPlugin(),
    new HtmlWebpackPlugin({template: './src/index.html'})
  ]
};
module.exports = config;

Mode

通过选择 development 或 production 之中的一个，来设置 mode 参数

webpack.config.js

module.exports = {
  mode: 'production'
};

mode.js

// webpack.development.config.js
module.exports = {
+ mode: 'development'
- plugins: [
-   new webpack.NamedModulesPlugin(),
-   new webpack.DefinePlugin({ "process.env.NODE_ENV": JSON.stringify("development") }),
- ]
}

// webpack.production.config.js
module.exports = {
+  mode: 'production',
-  plugins: [
-    new UglifyJsPlugin(/* ... */),
-    new webpack.DefinePlugin({ "process.env.NODE_ENV": JSON.stringify("production") }),
-    new webpack.optimize.ModuleConcatenationPlugin(),
-    new webpack.NoEmitOnErrorsPlugin()
-  ]
}

常用插件

HtmlWebpackPlugin:

Options

const HtmlWebpackPlugin = require('html-webpack-plugin');
new HtmlWebpackPlugin({ template: 'src/index.html', minify: true, hash: true })

CleanWebpackPlugin:

const CleanWebpackPlugin = require('clean-webpack-plugin');
new CleanWebpackPlugin(['dist'])

MiniCssExtractPlugin(ExtractTextPlugin)：

new MiniCssExtractPlugin({ filename: "[name].css",chunkFilename: "[id].css" })
module: {
    rules: [{
        test: /\.css$/,
        use: [
            MiniCssExtractPlugin.loader,
            'css-loader'
        ]}
    ]
}

SplitChunksPlugin:

module.exports = {
    mode: 'development',
    entry: {
        main: './src/index.js',
        vendors: 'lodash'
    },
    optimization: {
        splitChunks: {
            cacheGroups: {
                vendors: {
                    test: /[\\/]node_modules[\\/]/,
                    name: "vendors",
                    chunks: "initial"
                }
            }
        }
    }
}

配置示例

package

package.json

{
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "webpack-dev-server --open",
    "build": "webpack --config webpack.prod.js"
  },
  "devDependencies": {
    "babel-loader": "^7.1.4",
    "babel-preset-react": "^6.24.1",
    "babel-plugin-import": "^1.7.0",
    "clean-webpack-plugin": "^0.1.19",
    "css-loader": "^0.28.11",
    "html-webpack-plugin": "^3.2.0",
    "mini-css-extract-plugin": "^0.4.0",
    "webpack": "^4.8.3",
    "webpack-cli": "^2.1.3",
    "webpack-dev-server": "^3.1.4"
  },
  "dependencies": {
    "antd": "^3.5.2",
    "babel-plugin-syntax-dynamic-import": "^6.18.0",
    "express": "^4.16.3",
    "lodash": "^4.17.10",
    "react": "^16.3.2",
    "react-dom": "^16.3.2",
    "react-loadable": "^5.4.0",
    "react-redux": "^5.0.7",
    "react-router": "^4.2.0",
    "react-router-dom": "^4.2.2",
    "redux": "^4.0.0",
    "redux-logger": "^3.0.6",
    "redux-promise": "^0.6.0",
    "redux-saga": "^0.16.0",
    "redux-thunk": "^2.2.0"
  }
}

开发环境

const CleanWebpackPlugin = require('clean-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const path = require('path');
module.exports = {
    mode: 'development',
    entry: {
        main: './src/index.js',
    },
    devtool: 'inline-source-map',
    devServer: {
        contentBase: './dist'
    },
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: '[name].js',
    },
    module: {
        rules: [{
            test: /\.css$/,
            use: [
                MiniCssExtractPlugin.loader,
                'css-loader'
            ]
        }, {
            test: /\.(js|jsx)$/,
            loader: 'babel-loader',
            options: {
                presets: ['react'],
                plugins: [
                    ["import", { "libraryName": "antd", "style": "css" }]
                ]
            },
            exclude: /node_modules/
        }]
    },
    plugins: [
        new CleanWebpackPlugin(['dist']),
        new HtmlWebpackPlugin({ minify: true, hash: true }),
        new MiniCssExtractPlugin({ filename: "[name].css", chunkFilename: "[id].css" })
    ],
    optimization: {
        splitChunks: {
            cacheGroups: {
                common: {
                    test: /[\\/]node_modules[\\/]/,
                    name: "common",
                    chunks: "initial",
                    enforce: true
                },
            }
        }
    }
};

生产环境

const CleanWebpackPlugin = require('clean-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const path = require('path');
module.exports = {
    mode: 'production',
    entry: {
        main: './src/index.js',
    },
    devtool: 'source-map',
    devServer: {
        contentBase: './dist',
        host: '192.168.0.75'
    },
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: '[name].js',
    },
    module: {
        rules: [{
            test: /\.css$/,
            use: [
                MiniCssExtractPlugin.loader,
                'css-loader'
            ]
        }, {
            test: /\.(js|jsx)$/,
            loader: 'babel-loader',
            options: {
                presets: ['react'],
                plugins: []
            },
            exclude: /node_modules/
        }]
    },
    plugins: [
        new CleanWebpackPlugin(['dist']),
        new HtmlWebpackPlugin({ template: 'src/index.html', minify: true, hash: true }),
        new MiniCssExtractPlugin({ filename: "[name].css", chunkFilename: "[id].css" })
    ],
    externals: {
        lodash: '_',
        react: 'React',
        'react-dom': 'ReactDOM',
        antd: 'antd'
    },
    optimization: {
        splitChunks: {
            cacheGroups: {
                common: {
                    test: /[\\/]node_modules[\\/]/,
                    name: "common",
                    chunks: "initial",
                    enforce: true
                },
            }
        }
    }
};