I have an Angular project created with Angular CLI, so I have angular.json file for configuring the build.
I wanted to integrate PurgeCSS as it seems to be a great tool
You can simply run the following commands in your project root directory
npm i -D postcss-import postcss-loader postcss-scss
ng add ngx-build-plus
In angular.json, make the following replacements in "architect" section:
"builder": "@angular-devkit/build-angular:browser" with "builder": "ngx-build-plus:browser" under "build",
"builder": "@angular-devkit/build-angular:dev-server" with "builder": "ngx-build-plus:dev-server" under "serve",
"builder": "@angular-devkit/build-angular:karma" with "builder": "ngx-build-plus:karma" under "test",
You should also add "extraWebpackConfig": "webpack.config.js" under options in the respected sections.