How do I minify/uglify before ionic build?

Ionic Framework ionic-v3
1

I’ve read the @ionic/app-scripts/README.md and tried adding some flags to my package.json scripts but nothing seems to work. A little help please? What do I need to do to uglify, especially before a --release build.

Many thanks!

"scripts": {
    "clean": "ionic-app-scripts clean",
    "build": "ionic-app-scripts build",
    "ionic:build": "ionic-app-scripts build --uglifyjs",
    "ionic:serve": "ionic-app-scripts serve"
  },