gulp.js

const autoprefixer = require('gulp-autoprefixer');
const babelify     = require('babelify');
const babelPolyfill = require('babel-polyfill');
const browserify   = require('browserify');
const buffer       = require('vinyl-buffer');
const concat       = require('gulp-concat');
const gulp         = require('gulp');
const livereload   = require('gulp-livereload');
const minifyCSS    = require('gulp-minify-css');
const nodemon      = require('gulp-nodemon')
const rename       = require('gulp-rename');
const source       = require('vinyl-source-stream');
const sourcemaps   = require('gulp-sourcemaps');
const uglify       = require('gulp-uglify');

gulp.task('start', function () {
  nodemon({
    script: 'dist/server.js',
    env: { 'NODE_ENV': 'development' }
  })
})

gulp.task('buildJS', function () {
  // index.module.js is your main JS file with all your module inclusions
  return browserify({entries: [babelPolyfill, './src/index.module.js'], debug: true})
    .transform("babelify", { presets: ["es2015"] })
    .bundle()
    .pipe(source('index.js'))
    .pipe(buffer())
    // .pipe(sourcemaps.init())
    // .pipe(sourcemaps.init({loadMaps: true}))
    // .pipe(uglify())
    .pipe(sourcemaps.write('./maps'))
    .pipe(gulp.dest('./dist'))
    .pipe(livereload());
});

gulp.task('buildCSS', function(){
  return gulp.src('src/css/*.css')
  .pipe(minifyCSS())
  .pipe(autoprefixer('last 2 version', 'safari 5', 'ie 8', 'ie 9'))
  .pipe(concat('style.min.css'))
  .pipe(gulp.dest('dist'))
})

gulp.task('watch', function () {
    livereload.listen();
    gulp.watch('./src/**/*.js', ['buildJS']);
    gulp.watch('./src/css/*.css', ['buildCSS']);
});

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