webpack 4.0 快速构建项目

说起前端的自动化构建，除了grunt，gulp，目前最火的无疑就是webpack。webpack最大的优点在于它的模块化。在这里，将记录关于webpack4.0自动化构建项目的学习之路。

官网指南：https://www.webpackjs.com/guides/

一、新建项目

mkdir webpack-demo && cd webpack-demo

二、初始化项目

npm init -y

三、安装webpack

npm install webpack webpack-cli --save-dev

四、下载其他依赖

"devDependencies": {
    "clean-webpack-plugin": "^0.1.19",
    "extract-text-webpack-plugin": "^4.0.0-beta.0",
    "html-webpack-plugin": "^3.2.0",
    "css-loader": "^1.0.0",         
    "style-loader": "^0.21.0",
    "file-loader": "^1.1.11",
    "papaparse": "^4.6.0",
    "url-loader": "^1.0.1",
    "csv-loader": "^3.0.2",    //用于加载.csv和.tsv文件，如不用可删除  
    "xml-loader": "^1.2.1"     //用于加载.xml文件，如不用可删除  
  }

五、webpack.config.js配置——加载资源和打包

在根目录下新建webpack.config.js文件，示例代码如下：

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const CleanWebpackPlugin = require('clean-webpack-plugin');

module.exports = {
  entry: {
    app: './src/index.js'    //入口文件
  },
  plugins: [
    new CleanWebpackPlugin(['dist']),      
    new HtmlWebpackPlugin({
      template: __dirname + '/src/index.html',
      filename: 'index.html',
      inject: 'body'
    }),
    new ExtractTextPlugin(      //用于分离CSS
      'styles.css')
  ],
  output: {
    filename: '[name].bundle.js',
    path: path.resolve(__dirname, 'dist'),
    publicPath: '/'
  },
  module: {
    rules: [
      // 加载css
      {
        test: /\.css$/,
        use: ExtractTextPlugin.extract({     
          fallback: 'style-loader',
          use: 'css-loader'
        })
      },
      // 加载图片
      {
        test: /\.(png|svg|jpg|gif)$/,
        use: [{
          loader: 'url-loader',
          options: {
            name: 'images/[name]_[hash:4].[ext]',
            limit: 8192
          }
        }]
      },
      // 加载字体
      {
        test: /\.(woff|woff2|eot|ttf|otf)$/,
        use: [{
          loader: 'file-loader',
          options: {
            name: '[name].[ext]'
          }
        }]
      },
      // 加载除json外的其他数据文件，json不需要loader
      {
        test: /\.(csv|tsv)$/,
        use: [
          'csv-loader'
        ]
      },
      {
        test: /\.xml$/,
        use: [
          'xml-loader'
        ]
      }
    ]
  }
}

六、配置开发环境

配置开发环境主要满足以下两个需求：

• 打包源代码时，可以追踪到错误和警告在源代码中的原始位置
• 起一个简单的web服务器，当代码发生该懂事，能够实时重新加载并显示在浏览器

首先， 安装webpack-dev-server：

npm install --save-dev webpack-dev-server

然后，在webpack.config.js添加source-map和devServer，与entry同级：

devtool: 'inline-source-map',        
devServer: {
    contentBase: './dist'
},

运行

webpack-dev-server --open

> webpack-demo@1.0.0 start D:\01_Study\04-前端自动化构建\webpack-demo
> webpack-dev-server --open

clean-webpack-plugin: D:\01_Study\04-前端自动化构建\webpack-demo\dist has been removed.
i ｢wds｣: Project is running at http://localhost:8080/
i ｢wds｣: webpack output is served from /
i ｢wds｣: Content not from webpack is served from ./dist
i ｢wdm｣: wait until bundle finished: /
‼ ｢wdm｣: Hash: 6df00cf00946fea52aea
Version: webpack 4.16.4
Time: 9623ms

 ...

配置scripts命令：

在package.json中添加：

"scripts": {
    "start": "webpack-dev-server --open",
    "build": "webpack"
  },