Webpack 4 and Uglify Plugin (TypeError: Cannot read property 'length' of undefined)

问题:

I'm having problems with Webpack 4 on a Linux machine. The build works fine in dev mode, but fail in production. It also seems to be working on a windows machine. I did try do downgrade webpack to an older version and nothing.

Nodejs: v10.2.1

 *TypeError: Cannot read property 'length' of undefined* at node_modules/uglifyjs-webpack-plugin/dist/uglify/index.js:59         this.workers = workers === true ? _os2.default.cpus().length - 1 : Math.min(Number(workers) || 0, _os2.default.cpus().length - 1); 

packge.json

{   "name": "webpack-demo",   "version": "1.0.0",   "license": "MIT",   "scripts": {     "build": "webpack -p"   },   "devDependencies": {},   "dependencies": {     "@types/node": "^10.5.1",     "css-loader": "^0.28.11",     "global": "^4.3.2",     "node-sass": "^4.9.1",     "npm": "^6.1.0",     "sass-loader": "^7.0.3",     "style-loader": "^0.21.0",     "ts-loader": "^4.4.2",     "typescript": "^2.9.2",     "uglifyjs-webpack-plugin": "1.0.0-beta.2",     "webpack": "^4.15.1",     "webpack-cli": "^3.0.8"   } } 

webpack.config.js

const path = require('path'); const UglifyJsPlugin = require('uglifyjs-webpack-plugin'); var webpack = require('webpack'); module.exports = {     entry: './src/index.ts',     devtool: 'source-map',      mode: 'production',      module: {              rules: [{                  test: /\.tsx?$/,                  use: 'ts-loader',                  exclude: /node_modules/              },              {                  test: /\.scss$/,                  use: ['style-loader', 'css-loader', 'sass-loader'],                  exclude: /node_modules/              }             ],          },     resolve: {              extensions: ['.tsx', '.ts', '.js','.css','.scss']          },     plugins: [         new UglifyJsPlugin()     ],     output: {         path: path.resolve(__dirname, 'dist'),         filename: 'main.js'     } } 

回答1:

Setting mode to production in Webpack v4 should do enough optimisations, so there's no need to specifically require the Uglify plugin. Try remove uglifyjs-webpack-plugin and there's also no need for passing the -p flag for the build script.

If you want to customise the Uglify plugin, you can also do so in Webpack's optimization config, see https://webpack.js.org/configuration/optimization/

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');  module.exports = {   //...   optimization: {     minimizer: [       new UglifyJsPlugin({ /* your config */ })     ]   } }; 

Finally, I have a basic webpack v4 starter boilerplate with all the latest ecosystem on Github, take a look and see if it will help you or not

回答2:

I was able to make it work by just disabling uglify from the production build.

module.exports = {     optimization:{         minimize: false, // <---- disables uglify.         // minimizer: [new UglifyJsPlugin()] <----- if you want to customize it.     } } 

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