gulpfile.js

var gulp           = require('gulp'),
		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'),
		del            = require('del'),
		imagemin       = require('gulp-imagemin'),
		cache          = require('gulp-cache'),
		autoprefixer   = require('gulp-autoprefixer'),
		notify         = require("gulp-notify"),
		rsync          = require('gulp-rsync'),
		sourcemaps     = require('gulp-sourcemaps');

gulp.task('common-js', function() {
	return gulp.src([
		'app/js/common.js',
		])
	//.pipe(concat('common.min.js'))
	//.pipe(uglify()) // minify (optional)
	.pipe(gulp.dest('app/js'))
	.pipe(browserSync.reload({stream: true}));
});

gulp.task('js', function() {
	return gulp.src([
		'./app/libs/jquery/jquery-3.2.1.min.js',
		])
	.pipe(concat('scripts.min.js'))
	.pipe(sourcemaps.init())
	.pipe(uglify()) // minify (optional)
	.pipe(sourcemaps.write('./'))
	.pipe(gulp.dest('app/js'))
});

gulp.task('js-watch', ['js'], function (done) {
    browserSync.reload();
    done();
});

gulp.task('browser-sync', function() {
	browserSync({
		server: {
			baseDir: 'app'
		},
		notify: false,
		// tunnel: true,
		// tunnel: "projectmane", //Demonstration page: http://projectmane.localtunnel.me
	});
});

gulp.task('sass', function() {
	return gulp.src('app/sass/**/*.scss')
	.pipe(sourcemaps.init())
	.pipe(sass().on("error", notify.onError()))
	.pipe(rename({suffix: '.min', prefix : ''}))
	.pipe(autoprefixer(['last 15 versions']))
	//.pipe(cleanCSS()) // (optional)
	.pipe(sourcemaps.write('./'))
	.pipe(gulp.dest('app/css'))
	.pipe(browserSync.reload({stream: true}));
});

gulp.task('watch', ['sass', 'js', 'common-js', 'browser-sync'], function() {
	gulp.watch('app/sass/**/*.scss', ['sass']);
	gulp.watch('libs/**/*.js', ['js-watch']);
	gulp.watch('app/js/common.js', ['common-js']);
	gulp.watch('app/*.html', browserSync.reload);
});

// (optional)

gulp.task('imagemin', function() {
	return gulp.src('app/img/**/*')
	.pipe(cache(imagemin()))
	.pipe(gulp.dest('dist/img')); 
});

gulp.task('build', ['removedist', 'sass', 'js'], function() {

	var buildFiles = gulp.src([
		'app/*.html',
		'app/.htaccess',
		]).pipe(gulp.dest('dist'));

	var buildCss = gulp.src([
		'app/css/main.min.css',
		'app/css/main.min.css.map',
		]).pipe(gulp.dest('dist/css'));

	var buildJs = gulp.src([
		'app/js/scripts.min.js',
		'app/js/scripts.min.js.map',
		]).pipe(gulp.dest('dist/js'));

	var buildCommonJs = gulp.src([
		'app/js/common.js',
		]).pipe(gulp.dest('dist/js'));

	var buildFonts = gulp.src([
		'app/fonts/**/*',
		]).pipe(gulp.dest('dist/fonts'));

});

gulp.task('removedist', function() { return del.sync('dist'); });
gulp.task('clearcache', function () { return cache.clearAll(); });

gulp.task('default', ['watch']);