Post Css & Sass & RTL Gulp Config

gulpfile.js

const { src, dest, watch, series, task } = require('gulp');
const postcss = require('gulp-postcss');
const autoprefixer = require('autoprefixer');
const cssnext = require('cssnext');
const precss = require('precss');
const cssnano = require('cssnano');
const sass = require('gulp-sass');
const fontMagician = require('postcss-font-magician');
const rtlcss = require('rtlcss');
const rename = require('gulp-rename');

var processors = [
    autoprefixer,
    cssnext,
    precss,
    fontMagician,
];

var processors_rtl = [rtlcss].concat(processors);

function css_ltr(cb){
    cb();
    return src('./src/css/*.scss')
        .pipe(sass().on('error', sass.logError))
        .pipe(postcss(processors))
        .pipe(dest('./dest/css'))
        .pipe(postcss([cssnano]))
        .pipe(rename({ extname: '.min.css' }))
        .pipe(dest('./dest/css'));
}

function css_rtl(cb){
    cb();
    return src('./src/css/*.scss')
        .pipe(sass().on('error', sass.logError))
        .pipe(postcss(processors_rtl))
        .pipe(rename({ extname: '-rtl.css' }))
        .pipe(dest('./dest/css'))
        .pipe(postcss([cssnano]))
        .pipe(rename({ extname: '.min.css' }))
        .pipe(dest('./dest/css'));
}

task('watch', function () {
    return watch('./src/css/*.scss', series(css_ltr, css_rtl));
});


exports.default = series(css_ltr, css_rtl);

Run gulp to compile or gulp watch to auto compile while files are changed