gulpfile.js

const gulp = require('gulp');
const autoprefixer = require('gulp-autoprefixer');
const uglify = require('gulp-uglify');
const browserify = require('gulp-browserify');
const cleanCSS = require('gulp-clean-css');
const concat = require('gulp-concat');
const del = require('del');

function compress() {
    return gulp.src('./src/css/*.css')
        .pipe(concat('style.css'))
        .pipe(autoprefixer({
            browsers: ['last 4 versions'],
            cascade: false
        }))
        .pipe(cleanCSS())
        .pipe(gulp.dest('./dist/css'));
}

gulp.task('mainCss', compress);

function gulpJS() {
    return gulp.src(['./src/js/model.js','./src/js/view.js','./src/js/controller.js','./src/js/init.js'])
        .pipe(concat('bundle.js'))
        .pipe(browserify({transform: ['babelify'],}))
        .pipe(uglify())
        .pipe(gulp.dest('./dist/js/'));
}

gulp.task('mainJs', gulpJS);

function watch() {
    gulp.watch('./src/css/*.css', compress);
    gulp.watch('./src/js/*.js', gulpJS);
}

function clean() {
    return del([ 'dist' ]);
}

gulp.task('watch', watch,gulp.parallel( 'mainJs','mainCss'));

gulp.task('default',gulp.parallel( 'mainJs','mainCss'));