gulpfile.js

const { src, dest, parallel } = require('gulp');
const cleanCSS = require('gulp-clean-css');
const package = require('./package.json');
const uglify = require('gulp-uglify');
const rename = require('gulp-rename');

// Get Plugin Version from `package.json`
const pluginVersion = package.version;

async function deleteMinFiles() {
  const fs = require('fs');
  const path = require('path');

  fs.readdir('./assets/css/', (err, files) => {
    files.forEach(file => {
      if (file.endsWith('.min.css')) {
        fs.unlinkSync(path.join('./assets/css/', file));
      }
    });
  });

  fs.readdir('./assets/js/', (err, files) => {
    files.forEach(file => {
      if (file.endsWith('.min.js')) {
        fs.unlinkSync(path.join('./assets/js/', file));
      }
    });
  });
}

function minifyCss() {
  return src(['assets/**/*.css', '!assets/**/*/*.min.css'])
    .pipe(cleanCSS({ compatibility: 'ie8' }))
    .pipe(rename(function (path) {
      path.extname = '-' + pluginVersion + '.min.css';
    }))
    .pipe(dest('./assets'));
}

function minifyJs() {
  return src(['assets/**/*.js', '!assets/**/*/*.min.js'])
    .pipe(uglify())
    .pipe(rename(function (path) {
      path.extname = '-' + pluginVersion + '.min.js';
    }))
    .pipe(dest('./assets'));
}

exports.build = parallel(deleteMinFiles, minifyCss, minifyJs);