gulpfile.js

'use strict';

var gulpfile = require('gulp');
var babel = require('gulp-babel');

gulpfile.task('copy_src', function () {
  return gulpfile.src(['lib/**/*.js'], { base: '.' })
    .pipe(gulpfile.dest('build'));
});
gulpfile.task('copy_bin', function () {
  return gulpfile.src(['bin/**/*.js'], { base: '.' })
    .pipe(gulpfile.dest('build'));
});

gulpfile.task('compile-es6-src', function () {
  return gulpfile.src('lib/**/*.js')
    .pipe(babel({'plugins': ['babel-plugin-transform-amd-to-commonjs']}))
    .pipe(gulpfile.dest('build/js/lib'));
});
gulpfile.task('compile-es6-bin', function () {
  return gulpfile.src('bin/**/*.js')
    .pipe(babel({'plugins': ['babel-plugin-transform-amd-to-commonjs']}))
    .pipe(gulpfile.dest('build/js/bin'));
});

gulpfile.task('default', gulpfile.series(['compile-es6-src', 'compile-es6-bin']));