Styjun

I am trying to do the Uglify of my bundle js file using below

import webpack from 'webpack';
import path from 'path';
import ExtractTextPlugin from 'extract-text-webpack-plugin';

const GLOBALS = 
 'process.env.NODE_ENV': JSON.stringify('production'), //This global makes sure React is built in prod mode. https://facebook.github.io/react/downloads.html
 __DEV__: false // potentially useful for feature flags. More info: https://github.com/petehunt/webpack-howto#6-feature-flags
;

export default 
 debug: true,
 devtool: 'source-map', // more info:https://webpack.github.io/docs/build-performance.html#sourcemaps and https://webpack.github.io/docs/configuration.html#devtool
 noInfo: true, // set to false to see a list of every file being bundled.
 entry: './src/index',
 target: 'web',
 output: 
 path: __dirname + '/dist', // Note: Physical files are only output by the production build task `npm run build`.
 publicPath: '/',
 filename: 'bundle.js'
 ,
 devServer: 
 contentBase: './dist'
 ,
 plugins: [
 new webpack.optimize.OccurenceOrderPlugin(),
 new webpack.DefinePlugin(GLOBALS),
 new ExtractTextPlugin('styles.css'),
 new webpack.optimize.DedupePlugin(),
 new webpack.optimize.UglifyJsPlugin(
 uglifyOptions:
 output: 
 comments: false, // remove comments
 ,
 compress: 
 unused: true,
 dead_code: true, // big one--strip code that will never execute
 warnings: false, // good for prod apps so users can't peek behind curtain
 drop_debugger: true,
 conditionals: true,
 evaluate: true,
 drop_console: true, // strips console statements
 sequences: true,
 booleans: true,
 
 ,
 )
 ],
 module: 
 loaders: [
 test: /.js$/, include: path.join(__dirname, 'src'), loaders: ['babel'],
 test: /(.css)$/, loaders: ['style', 'css'],
 test: /.eot(?v=d+.d+.d+)?$/, loader: 'file',
 woff2)$/, loader: 'url?prefix=font/&limit=5000',
 test: /.ttf(?v=d+.d+.d+)?$/, loader: 'url?limit=10000&mimetype=application/octet-stream',
 test: /.svg(?v=d+.d+.d+)?$/, loader: 'url?limit=10000&mimetype=image/svg+xml',
 
 test: /.json$/,
 loader: 'json-loader'
 ,
 
 test: /.(png
 ]
 
;

i am getting the below error making build

ERROR in bundle.js from UglifyJs
SyntaxError: Unexpected token: operator (>) [./~/query-string/index.js:9,0]

I assume you're using npm query-sting package of the latest version 6 which is written using ES6 syntax and apparently UglifyJS version which is used by your webpack doesn't support this syntax (because apparently, you're using old Webpack version?). So instead you need to instal query-sting version 5. You can see this info on their README page in INSTALL section.

But which webpack version do you use? Because if you're using latest Webpack 4 you should use optimization.minimize config instead which supports ES6+ syntax.