Babelify Browserify and SASS Gulp

.babelrc

{
  "presets": ["es2015"]
}

gulpfile.js

'use strict';

var gulp        = require('gulp');
var rename      = require('gulp-rename');

var sass        = require('gulp-sass');
var autopre     = require('gulp-autoprefixer');
var cleanCSS    = require('gulp-clean-css');
var mmq         = require('gulp-merge-media-queries');

var source      = require('vinyl-source-stream');
var uglify      = require('gulp-uglify');
var browserify  = require('browserify');
var babelify    = require('babelify');
var buffer      = require('vinyl-buffer');
var sourcemaps  = require('gulp-sourcemaps');

// Watching scss/js files
gulp.task('watch', ['sass', 'javascript'], function () {
    gulp.watch("./assets/scss/**/*.scss", ['sass']);
    gulp.watch("./assets/js/**/*.js", ['javascript']);
});

// Compile sass into CSS & auto-inject into browsers
gulp.task('sass', function () {
    return gulp.src("./assets/scss/main.scss")
        .pipe(sass().on('error', sass.logError))
    	.pipe(autopre({
    	    browsers: ['last 2 versions'],
    	    cascade: false
    	}))
        .pipe(mmq({
            log: true
        }))
        .pipe(cleanCSS({ compatibility: 'ie8' }))
        .pipe(gulp.dest("./"))
});

gulp.task('javascript', function () {
    return browserify({entries: './assets/js/src/app.js', debug: true})
        .transform("babelify", { presets: ["es2015"] })
        .bundle()
        .pipe(source('app.js'))
        .pipe(buffer())
        .pipe(sourcemaps.init())
        .pipe(uglify())
        .pipe(sourcemaps.write('./js/maps/'))
        .pipe(gulp.dest('./'));
});

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

package.json

{
  "name": "",
  "version": "1.0.0",
  "dependencies": {},
  "devDependencies": {
    "babel": "^6.5.2",
    "babel-cli": "^6.18.0",
    "babel-preset-es2015": "^6.18.0",
    "babel-preset-es2016": "^6.16.0",
    "babel-preset-es2017": "^6.16.0",
    "babelify": "^7.3.0",
    "browserify": "^13.3.0",
    "del": "^1.1.1",
    "gulp": "^3.9.1",
    "gulp-autoprefixer": "3.1.1",
    "gulp-browserify": "^0.5.1",
    "gulp-cache": "~0.4.5",
    "gulp-clean-css": "^2.0.13",
    "gulp-merge-media-queries": "^0.2.1",
    "gulp-rename": "^1.2.2",
    "gulp-sass": "^2.3.2",
    "gulp-sourcemaps": "^2.4.0",
    "gulp-uglify": "^2.0.0",
    "vinyl-buffer": "^1.0.0",
    "vinyl-source-stream": "^1.1.0"
  },
  "license": "",
  "repository": {
    "type": "",
    "url": ""
  }
}