HMR

const { resolve } = require(‘path‘);
const HtmlWebpackPlugin = require(‘html-webpack-plugin‘);

module.exports = {
  entry: [‘./src/js/index.js‘,‘./src/index.html‘],
  output: {
    filename: ‘js/bundle.js‘,
    path: resolve(__dirname, ‘build‘)
  },
  module: {
    rules: [
      // loader的配置
      {
        // 处理less资源
        test: /\.less$/,
        use: [‘style-loader‘, ‘css-loader‘, ‘less-loader‘]
      },
      {
        // 处理css资源
        test: /\.css$/,
        use: [‘style-loader‘, ‘css-loader‘]
      },
      {
        // 处理图片资源
        test: /\.(jpg|png|gif)$/,
        loader: ‘url-loader‘,
        options: {
          limit: 8 * 1024,
          name: ‘[hash:10].[ext]‘,
          outputPath: ‘imgs‘
        }
      },
      {
        // 处理html中img资源
        test: /\.html$/,
        loader: ‘html-loader‘
      },
      {
        // 处理其他资源
        exclude: /\.(html|js|css|less|jpg|png|gif)/,
        loader: ‘file-loader‘,
        options: {
          name: ‘[hash:10].[ext]‘,
          outputPath: ‘media‘
        }
      }
    ]
  },
  plugins: [
    // plugins的配置
    new HtmlWebpackPlugin({
      template: ‘./src/index.html‘
    })
  ],
  mode: ‘development‘,
  devServer: {
    contentBase: resolve(__dirname, ‘build‘),
    compress: true,
    port: 3000,
    open: true,
    hot: true //开启HMR功能, 当修改了webpack配置，新配置要想生效，必须重新npx webpack服务
  }
};

import ‘../css/iconfont.css‘;
import ‘../css/index.less‘;
import print from ‘./b‘

console.log(‘index.js被加载‘)
print()

if (module.hot) { // 一旦 module.hot 为true，说明开启了HMR功能。 --> 让HMR功能代码生效
  module.hot.accept(‘./b.js‘, function () { //方法会监听 b.js 文件的变化，一旦发生变化，其他模块不会重新打包构建。
    print(); //会执行后面的回调函数
  });
}