const purify = require("purify-css") // Reference of all HTML files from root directory let content = ['./*.html']; // Reference of all CSS files from root directory let css = ['3rdparty/bulma/css/bulma.css', './app/app.css']; let files = { output: '../.intermediate/app.css', whitelist: ['is-multiple', 'is-loading', 'is-narrow', 'is-active', 'climate-zone'], minify: true, info: true }; purify(content, css, files, function (purifiedAndMinifiedResult) { console.log(purifiedAndMinifiedResult); });