gulpfile.js

var source = require('vinyl-source-stream');
var gulp = require('gulp');
var gutil = require('gulp-util');
var browserify = require('browserify');
var babelify = require('babelify');
var stringify = require('stringify');
var watchify = require('watchify');
var notify = require('gulp-notify');
var uglify = require('gulp-uglify');
var streamify = require('gulp-streamify');
var rename = require('gulp-rename');


function handleErrors() {
  var args = Array.prototype.slice.call(arguments);
  notify.onError({
    title: 'Compile Error',
    message: '<%= error.message %>'
  }).apply(this, args);
  this.emit('end'); // Keep gulp from hanging on this task
}

function buildScript(file, watch) {

  var props = {
    entries: ['./src/' + file],
    debug : false,
    transform:  [
      [ stringify, { extensions: ['.html'], minify: true }],
      [ babelify, {'presets': ['es2015']}]
    ],
    sourceType: 'module'
  };

  // watchify() if watch requested, otherwise run browserify() once
  var bundler = watch ? watchify(browserify(props)) : browserify(props);

  function rebundle() {
    var stream = bundler.bundle();
    return stream
      .on('error', handleErrors)
      .pipe(source(file))
      //.pipe( streamify(uglify()) )
      .pipe(rename(function (path) {
        path.basename = "angular-formly-mongoose";
      }))
      .pipe(gulp.dest('./dist'));
  }

  // listen for an update and run rebundle
  bundler.on('update', function() {
    rebundle();
    gutil.log('Rebundle...');
  });

  // run it once the first time buildScript is called
  return rebundle();
}

// run once
gulp.task('scripts', function() {
  return buildScript('index.js', false);
});

// run 'scripts' task first, then watch for future changes
gulp.task('default', ['scripts'], function() {
  return buildScript('index.js', true);
});