第一种方式：不推荐

    1. // webpack.config.js
    2. const { CleanWebpackPlugin } = require('clean-webpack-plugin')
    3. const CopyWebpackPlugin = require('copy-webpack-plugin')
    4. module.exports = (env, argv) => {
    5.     let config = {...} // 默认配置
    6.   if (env === 'production') {
    7.       config.mode = 'production'
    8.     config.plugins = [
    9.         ...config.plugins,
    10.       new CleanWebpackPlugin(),
    11.       new CopyWebpackPlugin(['public'])
    12.     ]
    13.   }
    14.   return config
    15. }

    第二种方式
    yarn add webpack-merge —dev

    1. // webpack.common.js
    1. // webpack.dev.js
    2. const common = require('./webpack.common.js')
    3. const merge = require('webpack-merge')
    5. module.exports = merge(common, {
    6.     mode: 'development'
    7. })
    1. // webpack.prod.js
    2. const common = require('./webpack.common.js')
    3. const merge = require('webpack-merge')
    4. const { CleanWebpackPlugin } = require('clean-webpack-plugin')
    5. const CopyWebpackPlugin = require('copy-webpack-plugin')
    7. module.exports = merge(common, {
    8.     mode: 'production',
    9.   plugins: [
    10.       new CleanWebpackPlugin(),
    11.     new CopyWebpackPlugin(['public'])
    12.   ]
    13. })

    webpack构建速度和打包体积优化策略：https://segmentfault.com/a/1190000021952886