I'm getting an error when trying to run my webpack for production.

ERROR in js/main.21dbce548a76ffc14cfb.js from UglifyJs
SyntaxError: Unexpected token: operator (>) [./~/tmi.js/lib/utils.js:3,0][js/main.21dbce548a76ffc14cfb.js:3529,20]

utils.js:3,0 (which is the same as in my minified js) is:

// Return the second value if the first value is undefined..
    get: (obj1, obj2) => { return typeof obj1 === "undefined" ? obj2 : obj1; },

So I assume from that the error is thrown because it's reading ES6 but it doesn't understand ES6? (The arrow function)

I don't see what's going wrong here, this is my webpack.config.js

// changed some loader syntax after reading
// /

const path = require(`path`);

const webpack = require(`webpack`);
const {UglifyJsPlugin} = webpack.optimize;

const CopyWebpackPlugin = require(`copy-webpack-plugin`);
const ExtractTextWebpackPlugin = require(`extract-text-webpack-plugin`);
const configHtmls = require(`webpack-config-htmls`)();

const extractCSS = new ExtractTextWebpackPlugin(`css/style.css`);

// change for production build on different server path
const publicPath = `/`;

// hard copy assets folder for:
// - srcset images (not loaded through html-loader )
// - json files (through fetch)
// - fonts via WebFontLoader

const copy = new CopyWebpackPlugin([{
  from: `./src/assets`,
  to: `assets`
}], {
  ignore: [ `.DS_Store` ]
});

const config = {

  entry: [
    `./src/css/style.css`,
    `./src/js/script.js`
  ],

  resolve: {
    // import files without extension import ... from './Test'
    extensions: [`.js`, `.jsx`, `.css`]
  },

  output: {
    path: path.join(__dirname, `server`, `public`),
    filename: `js/[name].[hash].js`,
    publicPath
  },

  devtool: `sourcemap`,

  module: {

    rules: [
      {
        test: /\.css$/,
        loader: extractCSS.extract([
          {
            loader: `css`,
            options: {
              importLoaders: 1
            }
          },
          {
            loader: `postcss`
          }
        ])
      },
      {
        test: /\.html$/,
        loader: `html`,
        options: {
          attrs: [
            `audio:src`,
            `img:src`,
            `video:src`,
            `source:srcset`
          ] // read src from video, img & audio tag
        }
      },
      {
        test: /\.(jsx?)$/,
        exclude: /node_modules/,
        use: [
          {
            loader: `babel`
          },
          {
            loader: `eslint`,
            options: {
              fix: true
            }
          }
        ]
      },
      {
        test: /\.(svg|png|jpe?g|gif|webp)$/,
        loader: `url`,
        options: {
          limit: 1000, // inline if < 1 kb
          context: `./src`,
          name: `[path][name].[ext]`
        }
      },
      {
        test: /\.(mp3|mp4)$/,
        loader: `file`,
        options: {
          context: `./src`,
          name: `[path][name].[ext]`
        }
      }
    ]

  },

  plugins: [
    extractCSS,
    copy
  ]

};

if(process.env.NODE_ENV === `production`){

  //image optimizing
  config.module.rules.push({
    test: /\.(svg|png|jpe?g|gif)$/,
    loader: `image-webpack`,
    enforce: `pre`
  });

  config.plugins = [
    ...config.plugins,
    new UglifyJsPlugin({
      sourceMap: true, // false returns errors.. -p + plugin conflict
      ments: false
    })
  ];

}

config.plugins = [...config.plugins, ...configHtmls.plugins];

module.exports = config;

I'm getting an error when trying to run my webpack for production.

ERROR in js/main.21dbce548a76ffc14cfb.js from UglifyJs
SyntaxError: Unexpected token: operator (>) [./~/tmi.js/lib/utils.js:3,0][js/main.21dbce548a76ffc14cfb.js:3529,20]

utils.js:3,0 (which is the same as in my minified js) is:

// Return the second value if the first value is undefined..
    get: (obj1, obj2) => { return typeof obj1 === "undefined" ? obj2 : obj1; },

So I assume from that the error is thrown because it's reading ES6 but it doesn't understand ES6? (The arrow function)

I don't see what's going wrong here, this is my webpack.config.js

// changed some loader syntax after reading
// https://webpack.js/how-to/upgrade-from-webpack-1/

const path = require(`path`);

const webpack = require(`webpack`);
const {UglifyJsPlugin} = webpack.optimize;

const CopyWebpackPlugin = require(`copy-webpack-plugin`);
const ExtractTextWebpackPlugin = require(`extract-text-webpack-plugin`);
const configHtmls = require(`webpack-config-htmls`)();

const extractCSS = new ExtractTextWebpackPlugin(`css/style.css`);

// change for production build on different server path
const publicPath = `/`;

// hard copy assets folder for:
// - srcset images (not loaded through html-loader )
// - json files (through fetch)
// - fonts via WebFontLoader

const copy = new CopyWebpackPlugin([{
  from: `./src/assets`,
  to: `assets`
}], {
  ignore: [ `.DS_Store` ]
});

const config = {

  entry: [
    `./src/css/style.css`,
    `./src/js/script.js`
  ],

  resolve: {
    // import files without extension import ... from './Test'
    extensions: [`.js`, `.jsx`, `.css`]
  },

  output: {
    path: path.join(__dirname, `server`, `public`),
    filename: `js/[name].[hash].js`,
    publicPath
  },

  devtool: `sourcemap`,

  module: {

    rules: [
      {
        test: /\.css$/,
        loader: extractCSS.extract([
          {
            loader: `css`,
            options: {
              importLoaders: 1
            }
          },
          {
            loader: `postcss`
          }
        ])
      },
      {
        test: /\.html$/,
        loader: `html`,
        options: {
          attrs: [
            `audio:src`,
            `img:src`,
            `video:src`,
            `source:srcset`
          ] // read src from video, img & audio tag
        }
      },
      {
        test: /\.(jsx?)$/,
        exclude: /node_modules/,
        use: [
          {
            loader: `babel`
          },
          {
            loader: `eslint`,
            options: {
              fix: true
            }
          }
        ]
      },
      {
        test: /\.(svg|png|jpe?g|gif|webp)$/,
        loader: `url`,
        options: {
          limit: 1000, // inline if < 1 kb
          context: `./src`,
          name: `[path][name].[ext]`
        }
      },
      {
        test: /\.(mp3|mp4)$/,
        loader: `file`,
        options: {
          context: `./src`,
          name: `[path][name].[ext]`
        }
      }
    ]

  },

  plugins: [
    extractCSS,
    copy
  ]

};

if(process.env.NODE_ENV === `production`){

  //image optimizing
  config.module.rules.push({
    test: /\.(svg|png|jpe?g|gif)$/,
    loader: `image-webpack`,
    enforce: `pre`
  });

  config.plugins = [
    ...config.plugins,
    new UglifyJsPlugin({
      sourceMap: true, // false returns errors.. -p + plugin conflict
      ments: false
    })
  ];

}

config.plugins = [...config.plugins, ...configHtmls.plugins];

module.exports = config;

• javascript
• webpack
• uglifyjs

• 2 You're not specifying presets in the babel section with query, so do you have .babelrc with "presets": ["es2015"] in it? – JJPandari Commented Nov 17, 2016 at 7:12
• @clk answer posted :3 – JJPandari Commented Apr 29, 2017 at 1:32
• Answer accepted :3 – Kevin Commented Apr 29, 2017 at 7:44

3 Answers 3

OP's error is from UglifyJs, as is solved in the accepted answer, some people to this page may get the error from babel, in which case, fix it with: add "presets": ["es2015"] either to the options.presets section of babel-loader, or to .babelrc.

UglifyJs2 has a Harmony branch which accepts ES6 syntax to be minified. At this moment, you need to create a fork of webpack and point webpack to that fork.

I recently answered a couple of similar questions. Please have a look at #38387544 or #39064441 for detailed instructions.

In my case I was using webpack version 1.14 I got help from git ref

steps:

1. install yarn add uglifyes-webpack-plugin (and removed yarn remove uglifyjs-webpack-plugin)
2. then install yarn add uglify-js-es6
3. In webpack.config.js file change new webpack.optimize.UglifyJsPlugin to new UglifyJsPlugin

then I was able to build. Thanks