Minimal gulpfile for building JS

gulpfile.js

/*
 * Copyright 2016 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

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

gulp.task('scripts', function() {
  return browserify({
    entries: 'index.js',  // this is your source, you need to write this file
  })
  .bundle()
  .pipe(source('index-compiled.js'))  // this is the output file name
  .pipe(gulp.dest('./'));  // write the file to this path (you could use dist/, output/, etc)
});

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