ds-site/gulpfile.js

const { src, dest, parallel, watch } = require('gulp');
const sass = require('gulp-sass');
const minifyCSS = require('gulp-csso');

const frontendSassFolder = 'Resources/Private/Sass/Frontend/';
const backendSassFolder = 'Resources/Private/Sass/Backend/';

function frontendCss() {
    return src(frontendSassFolder + 'index.scss')
        .pipe(sass({
            includePaths: [
                './node_modules/'
            ]
        }).on('error', sass.logError))
        .pipe(minifyCSS())
        .pipe(dest('Resources/Public/Css/'))
}
function backendCss() {
    return src(backendSassFolder + 'index.scss')
        .pipe(sass({
            includePaths: [
                './node_modules/'
            ]
        }).on('error', sass.logError))
        .pipe(minifyCSS())
        .pipe(dest('Resources/Public/Backend/Css/'))
}

exports.frontendCss = frontendCss;
exports.backendCss = backendCss;
exports.watch = function () {
    watch([frontendSassFolder + '**/*.scss'], {ignoreInitial: false}, frontendCss);
    watch([backendSassFolder + '**/*.scss'], {ignoreInitial: false}, backendCss);
};
exports.default = parallel(frontendCss, backendCss);