gulpfile.coffee Gulp + Browserify & Watchify & Externals

gulp = require 'gulp'
watchify = require 'watchify'
browserify = require 'browserify'
source = require 'vinyl-source-stream'
buffer = require 'vinyl-buffer'
gutil = require 'gulp-util'
assign = require 'lodash.assign'
rename = require 'rename'

EXTERNALS = [
  {'require': 'jquery', expose: '$'},
]

opts =
  entries: ['./src/index.coffee']
  debug: true
  extensions: ['.js', '.coffee']
  bundleExternal: false

b = watchify(browserify(assign {}, watchify.args, opts))
.transform("coffeeify")
.plugin("minifyify", {
    output: 'js/index.js.map'
    map: 'index.js.map'
  })

bundle = ->
  b.bundle()
  .on('error', gutil.log.bind(gutil, 'Browserify Error'))
  .pipe(source('index.js'))
  .pipe(buffer())
  .pipe(gulp.dest('./js'))

b.on 'update', bundle
b.on 'log', gutil.log

gulp.task 'libs', ->
  vb = browserify('./src/vendor.coffee', debug: true)
  .plugin("minifyify", output: 'js/vendor.js.map', map: 'index.js.map')

  EXTERNALS.forEach (x) ->
    if x.expose?
      vb.require x.require, expose: x.expose
      b.external x.require, expose: x.expose
    else
      vb.require x.require
      b.external x.require

  watchify(vb)
  .bundle()
  .pipe(source('vendor.js'))
  .pipe(gulp.dest("./js"))

gulp.task 'default', ['libs'], bundle