gulpfile.js

var gulp          = require('gulp'),
		gutil         = require('gulp-util' ),
		sass          = require('gulp-sass'),
		browserSync   = require('browser-sync'),
		concat        = require('gulp-concat'),
		uglify        = require('gulp-uglify'),
		cleancss      = require('gulp-clean-css'),
		rename        = require('gulp-rename'),
		autoprefixer  = require('gulp-autoprefixer'),
		notify        = require('gulp-notify');

gulp.task('browser-sync', function() {
	browserSync({
		server: {
			baseDir: 'app'
		},
		notify: false,
		open: false,
		// online: false, // Work Offline Without Internet Connection
		// tunnel: true, tunnel: "projectname", // Demonstration page: http://projectname.localtunnel.me
	})
});

gulp.task('styles', function() {
	return gulp.src('app/scss/**/*.scss')
	.pipe(sass({ outputStyle: 'expanded' }).on("error", notify.onError()))
	.pipe(rename({ suffix: '.min', prefix : '' }))
	.pipe(autoprefixer({
		grid: true,
		overrideBrowserslist: ['last 10 versions']
	}))
	.pipe(cleancss( {level: { 1: { specialComments: 0 } } })) // Opt., comment out when debugging
	.pipe(gulp.dest('app/css'))
	.pipe(browserSync.stream())
});

gulp.task('libs-js', function() {
	return gulp.src([
		'app/libs/jquery/dist/jquery.min.js'
	])
	.pipe(concat('libs.min.js'))
	.pipe(uglify())
	.pipe(gulp.dest('app/js'))
});

gulp.task('code', function() {
	return gulp.src(['app/*.html', 'app/js/*.js'])
	.pipe(browserSync.reload({ stream: true }))
});

gulp.task('watch', function() {
	gulp.watch('app/scss/**/*.scss', gulp.parallel('styles'));
	gulp.watch(['app/*.html', 'app/js/*.js'], gulp.parallel('code'));
});

gulp.task('default', gulp.parallel('styles', 'libs-js', 'browser-sync', 'watch'));