css.js

css.js

/* import all 3 libraries and file system for writing the final file */
var sass = require('node-sass');
var CleanCSS = require('clean-css');
var uncss = require('uncss');
var fs = require('fs');

/* compile scss files */
// you need to set 'filename' to a string of the path to your main scss file
sass.render({file: filename}, function(err, result) { 
  if (err) {
    console.log(err); 
    return;  
  }
  /* minify results */
  var output = new CleanCSS({}).minify(result);

  /* remove unused css */
  // you need to set 'files' to an array of strings, 
  // each string being a relative path or url to an HTML file
  uncss(files, {}, function (error, output) {
    fs.writeFile("readyForProduction.css", output, function(err) {
        if (err) {
            console.log(err);
        }
    });
  });
});