webpack4 配置 ssr 环境遇到“document is not defined”

{
  "vue-loader": "^15.4.2",
  "mini-css-extract-plugin": "^0.4.3",
  "webpack": "^4.20.2",
  "webpack-cli": "^3.1.2"
  ...
}

# 基本配置
const path = require('path')
const webpack = require('webpack')
const {VueLoaderPlugin} = require('vue-loader')
const FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')

const resolve = dir => path.join(__dirname, '../', dir)
const isProd = process.env.NODE_ENV === 'production'

const base = {
 mode: isProd ? 'production' : 'development',
 devtool: isProd ? false : 'cheap-eval-source-map',
 output: {
  path: path.resolve(__dirname, '../dist'),
  publicPath: '/dist/',
  filename: '[name].[chunkhash].js'
 },
 resolve: {
  alias: {
   'vue$': 'vue/dist/vue.esm.js',
   'public': path.resolve(__dirname, '../public')
  }
 },
 module: {
  noParse: /es6-promise\.js$/, // avoid webpack shimming process
  rules: [
   {
    test: /\.vue$/,
    loader: 'vue-loader',
    include: resolve("src")
   },
   {
    test: /\.js$/,
    loader: 'babel-loader',
    exclude: file => (
     /node_modules/.test(file) && !/\.vue\.js/.test(file)
    )
   },
   {
    test: /\.(png|jpg|gif|svg)$/,
    loader: 'url-loader',
    options: {
     limit: 10000,
     name: '[name].[ext]?[hash]'
    }
   }
  ]
 },
 plugins: setPlugin()
}

function setPlugin() {
 const base = [new VueLoaderPlugin()]
 const dev = [new FriendlyErrorsPlugin()]
 const prod = []
 return base.concat(isProd ? prod : dev)
}

module.exports = base;

# 只展示先关配置
const webpack = require('webpack')
const merge = require('webpack-merge')
const base = require('./webpack.base.config')
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const VueSSRClientPlugin = require('vue-server-renderer/client-plugin')

const isProd = process.env.NODE_ENV === 'production'

const config = merge(base, {
 module: {
  rules: [
   {
    test: /\.styl(us)?$/,
    use: [
     isProd ? MiniCssExtractPlugin.loader : 'vue-style-loader',
     {
      loader: 'css-loader'
     },
     'stylus-loader'
    ],
   },
   {
    test: /\.(le|c)ss$/,
    use: [
     isProd ? MiniCssExtractPlugin.loader : 'vue-style-loader',
     {
      loader: 'css-loader'
     },
     'less-loader',
    ],
   }
  ]
 },
 plugins: [
  new MiniCssExtractPlugin({
   filename: isProd ? '[name].[chunkhash].css' : '[name].css',
   chunkFilename: isProd ? '[id].[chunkhash].css': '[id].css',
  }),
  new VueSSRClientPlugin()
 ]
})

module.exports = config

# 只展示先关配置
const webpack = require('webpack')
const merge = require('webpack-merge')
const base = require('./webpack.base.config')
const VueSSRServerPlugin = require('vue-server-renderer/server-plugin')

module.exports = merge(base, {
 target: 'node',
 module: {
  rules: [
   {
    test: /\.styl(us)?$/,
    use: [
     'vue-style-loader',
     {
      loader: 'css-loader'
     },
     'stylus-loader'
    ],
   },
   {
    test: /\.(le|c)ss$/,
    use: [
     'vue-style-loader',
     {
      loader: 'css-loader'
     },
     'less-loader',
    ],
   }
  ]
 },
 plugins: [
  new VueSSRServerPlugin()
 ]
})