write-file.js

module.exports = function (path, opts) {

  return function (err, src) {

    if (!opts) opts = {}

    if (!path) throw new Error('Path must be provided')

    if (err) {
      throw err
    }

    fs.writeFileSync(path, src, 'utf8');
    if (opts.debug) console.log('writing to ' + path)
  });

}

to use:

var writer = require('./write-file')
var path = require('path')

var write = writer(path.join(__dirname, 'bundle.js'), {debug: true})

write(null, src) // writes the file