New ES6 project with Babel, Browserify & Gulp + Bundling/Watching Multiple Files

gulpfile.babel.js

import gulp from 'gulp';
import sourcemaps from 'gulp-sourcemaps';
import buffer from 'gulp-buffer';
import uglify from 'gulp-uglify';
import tap from 'gulp-tap';
import browserify from 'browserify';
import babel from 'babelify';

gulp.task('build', () => {

  return gulp.src('./assets/js/*.js', { read: false })
    .pipe(tap((file) => {
      file.contents = browserify(file.path, {
        debug: true
      }).transform(babel, {
        presets: [ 'es2015' ]
      }).bundle();
    }))
    .pipe(buffer())
    .pipe(sourcemaps.init({ loadMaps: true }))
    .pipe(uglify())
    .pipe(sourcemaps.write('./'))
    .pipe(gulp.dest('./public/assets/js/'));
});

gulp.task('watch', function () {
  gulp.watch('./assets/js/**/*.js', ['build']);
});

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