replaced UglifyJsPlugin with TerserPlugin

webpack.config.js

@@ -1,4 +1,4 @@
-const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
+const TerserPlugin = require('terser-webpack-plugin');
 const CopyPlugin = require('copy-webpack-plugin');
 const path = require('path');
 
@@ -27,15 +27,23 @@ module.exports = (env, argv) => {
     },
     optimization: {
       minimizer: [
-        // we specify a custom UglifyJsPlugin here to get source maps in production.
-        new UglifyJsPlugin({
-          cache: true,
-          parallel: true,
-          uglifyOptions: {
-            compress: true,
-            mangle: true
+        new TerserPlugin({
+          sourceMap: true,
+          terserOptions: {
+            ecma: undefined,
+            warnings: false,
+            parse: {},
+            compress: {},
+            mangle: true, // Note `mangle.properties` is `false` by default.
+            module: false,
+            output: null,
+            toplevel: false,
+            nameCache: null,
+            ie8: false,
+            keep_classnames: undefined,
+            keep_fnames: false,
+            safari10: false,
           },
-          sourceMap: true
         })
       ]
     },