ES6

foo.js

// javascripts/components/foo.js

export default function() {
  console.log('foo');
}

gulpfile.js

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

var paths = {
  js: {
    file: 'main.js',
    src: './javascripts/main.js',
    watch: './javascripts/**/*.js',
    dist: './assets',
    output: './assets/main.js',
  }
};

gulp.task('js', function() {
  return browserify({ entries: paths.js.src, debug: true })
    .transform(babelify)
    .bundle()
    .pipe(source(paths.js.file))
    .pipe(gulp.dest(paths.js.dist));
});

main.js

// javascripts/main.js

import foo from './components/foo';

// logs foo
foo();

I've commented their file locations as Github wouldn't let me specify them in the file name.

I stole this from: http://advantcomp.com/blog/ES6Modules/