Gulpfile to transpile ES6 using babel and browserify

gulpfile.js

// npm install --save-dev gulp gulp-babel babelify through2 gulp-rename gulp-load-plugins

var gulp = require('gulp');
var $ = require('gulp-load-plugins')();
var browserify = require('browserify');
var through2 = require('through2');
var babelify = require('babelify');

var srcApp = './src/app.js';
var srcWatchPath = './src/**/*.js'
var distAppPath = './dist';
var distAppFile = 'app.js';

gulp.task('build', function() {
  return gulp.src(srcApp)
    .pipe(through2.obj(function(file, enc, next) {
      browserify(file.path, {
          debug: process.env.NODE_ENV === 'development'
        })
        .transform(babelify)
        .bundle(function(err, res) {
          if (err) return next(err);

          file.contents = res;
          next(null, file);
        });
    }))
    .on('error', function(error) {
      console.log(error.stack);
      this.emit('end');
    })
    .pipe($.rename(distAppFile))
    .pipe(gulp.dest(distAppPath));
});


gulp.task('watch', function() {
  gulp.watch(srcWatchPath, ['build']);
});

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