webpack.config.js

new UglifyJsPlugin({
  uglifyOptions: {
    compress: {
      arrows: false,
      booleans: false,
      cascade: false,
      collapse_vars: false,
      comparisons: false,
      computed_props: false,
      hoist_funs: false,
      hoist_props: false,
      hoist_vars: false,
      if_return: false,
      inline: false,
      join_vars: false,
      keep_infinity: true,
      loops: false,
      negate_iife: false,
      properties: false,
      reduce_funcs: false,
      reduce_vars: false,
      sequences: false,
      side_effects: false,
      switches: false,
      top_retain: false,
      toplevel: false,
      typeofs: false,
      unused: false,

      // Switch off all types of compression except those needed to convince
      // react-devtools that we're using a production build
      conditionals: true,
      dead_code: true,
      evaluate: true,
    },
    mangle: true,
  },
}),