perf: improve uglify plugin options

lib/builder/webpack/client.config.js

@@ -136,20 +136,23 @@ export default function webpackClientConfig() {
 
     // Minify JS
     // https://github.com/webpack-contrib/uglifyjs-webpack-plugin
-    config.plugins.push(
-      new UglifyJSPlugin({
-        cache: true,
-        sourceMap: true,
-        extractComments: {
-          filename: 'LICENSES'
-        },
-        uglifyOptions: {
-          output: {
-            comments: /^\**!|@preserve|@license|@cc_on/
+    if (this.options.build.uglify !== false) {
+      config.plugins.push(
+        new UglifyJSPlugin(Object.assign({
+          cache: true,
+          sourceMap: true,
+          parallel: true,
+          extractComments: {
+            filename: 'LICENSES'
+          },
+          uglifyOptions: {
+            output: {
+              comments: /^\**!|@preserve|@license|@cc_on/
+            }
           }
-        }
-      })
-    )
+        }, this.options.build.uglify))
+      )
+    }
 
     // Webpack Bundle Analyzer
     if (this.options.build.analyze) {

lib/common/options.js

@@ -198,6 +198,7 @@ Options.defaults = {
     extractCSS: false,
     cssSourceMap: undefined,
     ssr: undefined,
+    uglify: {},
     publicPath: '/_nuxt/',
     filenames: {
       css: 'vendor.[contenthash].css',