prepare dependencies

build/webpack.dist.prod.config.js

@@ -3,6 +3,7 @@ const webpack = require('webpack');
 const merge = require('webpack-merge');
 const webpackBaseConfig = require('./webpack.base.config.js');
 const CompressionPlugin = require('compression-webpack-plugin');
+const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
 
 process.env.NODE_ENV = 'production';
 
@@ -32,7 +33,7 @@ module.exports = merge(webpackBaseConfig, {
         new webpack.DefinePlugin({
             'process.env.NODE_ENV': '"production"'
         }),
-        new webpack.optimize.UglifyJsPlugin({
+        new UglifyJsPlugin({
             parallel: true,
             sourceMap: true,
         }),