https://gulpjs.com/ 

const { src, dest, parallel } = require('gulp');

const pug = require('gulp-pug');

const less = require('gulp-less');

const minifyCSS = require('gulp-csso');

const concat = require('gulp-concat');

function html() {

  return src('client/templates/*.pug')

    .pipe(pug())

    .pipe(dest('build/html'))

}

function css() {

  return src('client/templates/*.less')

    .pipe(less())

    .pipe(minifyCSS())

    .pipe(dest('build/css'))

}

function js() {

  return src('client/javascript/*.js', { sourcemaps: true })

    .pipe(concat('app.min.js'))

    .pipe(dest('build/js', { sourcemaps: true }))

}

exports.js = js;

exports.css = css;

exports.html = html;

exports.default = parallel(html, css, js);