Gulp with babelify, browserify and browsersync

javascript

var gulp = require('gulp');
var browserify = require('browserify');
var babelify = require('babelify');
var fs = require("fs");
var transform = require('vinyl-transform');
var browserSync = require('browser-sync');

gulp.task('serve', ['es6'], function() {
    browserSync({
        server: {
            baseDir: "./"
        },
        port: process.env.PORT || 4000
    });

    gulp.watch('app.js', ['es6']);
    gulp.watch("./*.*").on('change', browserSync.reload);

});

gulp.task('es6', function(){

    var b = browserify({
        debug: true
      });

    return b.transform(babelify)
        .require("./app.js", { entry: true })
        .bundle()
        .on("error", function (err) { console.log("Error: " + err.message); })
        .pipe(fs.createWriteStream("./bundle.js"));
});

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